Hi, Rachel. I critique each photo harshly so don't take anything personally.. I just get tired of 'great photo' comments so I hope I can offer something useful instead.
1. Lovely. Not a lot to complain about here... maybe you could've removed a few of the stray leaves in the frame (railing, lower right). Also you could've asked her to straighten her jeans. I see some sharpening artifacts but that is probably just from your web export.
2. Another good one. I'm not a fan of tree trunks in photos shooting up through the frames but it doesn't bother a lot of people.
3. I think you need to move your flash off-camera. All I can see with these next few is the on-camera fill but it wasn't enough -- generally the backgrounds are bright. The flatness from the on-camera fill isn't doing anything for facial structure or form. I also think they should be right on the grass and not on a distracting white blanket (though it probably added some fill!).
4. Nice expression and lighting from the side but the on-camera fill does it in for me. Also the trees in the background create another issue. You could've gone up on a ladder and shot down to eliminate them or it also looks like the two big ones could be photoshopped out if you have a few minutes.
5. A bit hot and the pose doesn't look natural. Sitting on the post doesn't look comfortable. Nice colours in the bkg.
6. The fence is blowing out here; on-camera flash wasn't enough. I think there is a better composition here, maybe if you're all 3 down on the ground with the railings as that would eliminate the trees again. Love the emotion here.
7. I like this concept; works well. I don't like the trees but not much you can do when you have to get this flare angle.
8. Very nice! I like this a lot... no flash... though her shoulder is a bit hot that could easily be burned down.
Do you use reflectors? Have you tried the flash off camera? You probably can't go through an umbrella when you're fighting the direct sun unless you get more power but even having it off to the side up on a stand will give you a lot more form to the faces when you have to use fill. I do think these are well done overall and when posted on Facebook should get you even more referrals.