I think there are ways of doing it that are respectful of her boundaries but also mean you have some photos.
When I was a child and teenager my Dad was a really keen amateur photographer (he had a dark room for a while). He took loads of photos, or loads for the days of film cameras anyway!
We were all a bit fed up of it, holiday photos weren't a problem as he was happy to take scenery shots or animated ones from a distance, but if he'd got almost to the end of a roll of film and wanted to take some portraits to use the end of the film there would be loads of eye rolling.
However looking back now I am so glad he did this. I look back and love to see some of those photos of when I was young, slim and lovely! My Mum says similar of the ones she hated having taken when they were first married.
I even like seeing the one that I can vividly remember hating him taking, because I was 15 and had a massive zit and a shiny forehead (or so I thought). I'm actually in the act of rolling my eyes!
Perhaps you could explain that you would like some photos and she might like them in future. Many of my friends have no photos of them as teenagers and now wish they did.
Tell her that you won't show anyone or display them without agreement and ask her what would make her feel comfortable about it. Perhaps she would like the chance to get ready and pose or even to do a selfie with you or maybe she'd prefer not to know you are taking the photo. Perhaps there is something specific she doesn't like about your photos and you could agree to do something different. Maybe she would feel more comfortable if someone else took a photo of the two of you together.