First, I want to preface this with the disclaimer that I am not a people shooter. I shoot products. That said, I am also a graphic designer and illustrator so my eye is a bit more refined than the casual photographer. That said, here are some takeaways from this that may be helpful.
Camera technique-wise, you nailed it. Lighting overall is balanced, especially in harsh light. Tones are managed and aside from some slight blur in the fur of #5, they all look nice and crisp for a windy day.
That said, if these are to be used as a professional portfolio, you might consider learning from these to really up your game. They're almost there and it's the little details that will take these from adequate to perfect. I'm sorry if the following comes across as nitpicky but this is how we grow in this business, right?
I will take into consideration that the two of you have little experience in this field. However, as your friend is looking to get into the fashion industry, she needs to learn this (NEEDS!) and the sooner she gets it, the better off she will be. Also, many of the things I see have also been pointed out by others so reiterating may stress the need to correct the issues.
Semantics on this thread aside, proper terminology is important to understand in any industry. It keeps confusion down to a minimum, as you saw.
Even though this was a 'favor' and the two of you did this on barebones budget, that doesn't mean production level should drop. I'm sure you now understand the frustrations of working on location without help. Enlist others to help; boy/girlfriends, buddies, family, others who would benefit from a free photo shoot. Get a hairdresser/MUA to join in and shoot images for their portfolios while you're at it in return for their help. You'd be surprised how many people you can get to help for free. The two of you will get experience running a production photo shoot in the process.
A mood board was mentioned and is vital to place everyone on the same train of thought (even if it's two people). That way when the time comes to shoot everyone knows exactly what the look and feel of each shot will be. It'll also be less stress on you because you won't have to wrack your brain to, "come up with something," on the spot. I like to use Pinterest for creating my mood boards as it is easy to use, accessible by all production members and has an almost endless talent pool to resource.
I feel this shoot was of greater value to your friend than to you but that doesn't mean you can't learn from it also. Photographing fashion is not the same as photographing people, even though there are people in the clothes. Whether editorial, catalog, runway or any other derivative of the genre, it is all about the clothing. How it flows on the body, the textures, a special feature and any number of things. The model's job is to showcase that outfit to its best appearance, which is trickier than it sounds. I know, I modeled in my 20's. Wrinkles, folds, button lines, zippers all need to lay flat, collars and sleeves can't have unusual twists. Etc. That's why working with a stylist is nice. It's an extra set of eyes to look out for problem areas,
End use of any image is crucial to keep in mind. Whether it's for a publication, online catalog or personal portfolio, the images need to be shot to the need. Cropping is more important for fashion than for portraiture since cropping out some parts of a garment can ruin the shot, whereas that same crop in portraiture can be of benefit. For example. as a portfolio piece, the first image would have been stronger if the entire outfit had been seen in whole. Since it appears to be an ensemble piece, I now can't tell if this is a long skirt or a short one. If this is her piece she designed, she would want the complete story told, not just part of it. Also, personal taste but something to consider here, the tattoo on her ribs detracts from the outfit. That should be edited out. You don't want something that competes for the viewer's attention. Specially for a design student looking to get her work noticed.
A note about the incongruence of a bathing suit in the savannah has already been mentioned but I will add that incongruence is not necessarily a bad thing when used properly. The proper conveyance of mood can sometimes trump utility in such cases. Sometimes. Other times it can have the viewer ask, "what is going on here? It doesn't make sense."
In that vein of thought, textures are also important. For fashion design, texture is a key element when assembling an outfit. The same care should be taken when placing that outfit into an environment. For example, in the third image, the texture of the foreground strongly competes with the texture of the outfit. As a result, the outfit suffers for it. Other techniques could have been utilized to compensate for that error in that image, like lighting to minimize the foreground, different angle of view, or a different pose. You get the meaning.
The last tip is rather general in nature but one that I see done often in many areas of photography. Let me see if I can explain it right...
Any action/decision/pose must be deliberate AND it must convey that purpose to the viewer (whether it's obvious or subliminal). There needs to be a reason for it, whether it is to present a subject better, to highlight a feature, to express a mood, etc. While some may argue this point I can site way too many example why this is important to keep in mind. I'll use a simple, but common, example. A landscape where the horizon line has a 5 or 10 degree angle to it looks off. A photographer can 'claim' it was done on purpose but to everyone else it reads as being wrong. Put a 25, 30 or even a 45 degree angle to it and there is no question that was by choice with an identifiable result. Drama. A portrait where the photographer uses a wide angle lens causes the nose to be exaggerated and the face made to look bigger than it is. Again, one can 'claim' it was done on purpose but for a standard portrait we all know that a big no-no. However, have the person exaggerate their facial expression into the lens and add a crazy perspective and suddenly that image has impact.
Both those example illustrate how deliberate actions convey a stronger image. The same holds true for your images here. Some border on being more dramatic but lack that extra push. Unfortunately there are just too many techniques that can be used to get more 'pow' to detail here. What I will suggest, though, is to challenge yourself in situations like this. Here is a golden opportunity to experiment. Shoots like this should not be about sticking to what you are comfortable with, save that for paying gigs where you can't afford to look like a novice . Yes, you should maintain a level of control which resides well within your comfort zone, and that is always a good place to start. But, since there is really no pressure to deliver within boundaries, take that opportunity to stretch yourself. Try things you are uncomfortable with. Get in extra close, or back off far way. Add props, encourage the model to push herself as well. Make it fun. Tell dumb jokes or make a fool out of yourself to get the mood to change on set. Shoot the same scene with different lenses at different focal lengths. Have the model move in the setting to add action. Move the camera to add blur. Etc., etc., etc.
Here is a lesson I teach quite often across multiple disciplines. There is power in contrast and comparison. If I give you a lollipop and tell you it's the best in the world but you have never tasted a lollipop, you wouldn't know if it was or wasn't the best. You have no measure of comparison. It's not until you've tasted hundreds of lollipops that you would be able to confirm (or deny) that claim. The same goes with images. Until you have pushed some limits would you know where along that limit an image looks great. Too often we see what appears to be a great image until we compare it against its contemporaries that we realize our image is bland. That's because we haven't pushed ourselves.
Anyhow, overall they are good images, as I said. But to be commercially viable in a professional portfolio, either yours or hers, the ante needs to be raised. But, at least now you have something to compare against and the next time you have no reason not to raise your own bar.
These are just my two bits. Hope some of my observations helped.