It would be really easy to get all self-righteous and offer condescending advice but the bottom line is that yeah, it can be a little irking.
From another perspective, its a lot to expect of her to automatically know the etiquette.
You seem to have a choice of:
- Finding it within yourself to let it go.
- Gently mention to her that it's customary to give photo credit.
- Keep festering over it and carry that emotional baggage.
Let's walk thru option 2 for a moment. You can just mention it and let her find her own way to the righteous path. However if she doesn't then comply, well, your festering will crank up the volume about 20x.
In addition, even if she does comply, there's a strong chance that she won't truly see it from your side and it'll be the source of a new private dislike of you. If it goes that route, she'll see you as petty.
Option 3 isn't exactly good for your Zen.
Back to Option 1. The cosmic go-around will reward you some day for your generosity. Maybe not even from her, but somebody, some day, will notice that or similar generous selfless deeds and at the least, they'll form a great opinion of you.
You may not even learn of their high opinion, but it'll be out there and good things will flow your way as a result.
Your call...
At the end of the day, the problem is your own doing for not setting this straight up-front. You could have either mentioned it to mentally prepare them as an informal condition of your efforts. Or; you could even put a logo on each photo. Then everyone would know even without them having to make mention. If they cropped your logo off every photo, well, then you'd have a legitimate beef with them to decide whether or not to pursue. So; lesson learned...