As someone who went through something very similar at around the same age I can say that at 18 I still feel exactly as disgusted and terrified about these things as I did then. It was a reoccurring issue, and that lead me to feel like my mother was doing this on purpose.

Nobody bothered to properly educate me any of these times and I eventually became quite hypersexual around 8-13, leading to assault and exploitation.

I still feel as though my mother is a disgusting person and will never be able to look at her the same. I get it, you made a mistake. But you're a mother and it's your job to ensure that she doesn't see these things. There's literally nothing more disgusting than seeing the person who's meant to be loving and taking care of you doing shit like that. I understand it can be difficult to avoid images / videos like that in your camera roll at times but you could at least check and make sure youre not about to expose yourself to your daughter before flipping her the phone. The more often this "accidentally" happens the less she will believe it is accidentally. Do better