Oh god I really feel for you, my mum is like this too, she just can't help herself.
When I lived at home she'd go through my room monthly without telling me, thinking she was incredibly clever and sneaky but always failing to put things back correctly.
She found my "secret underwear bag" when I was 17 
. I know this because I stapled the fecker shut and put a sticker on it saying "Mum, this is private. Please leave it alone". About 2 weeks later it was completely ripped open and put back where she'd found it. I moved out a week after that and said NOTHING. Incidentally, the DP the underwear was for is still my DP now 10 years on! 
Our relationship struggled for a very long time as she couldn't understand why I wanted to live at DP's mums house and not hers. Eventually, I told her that it was because I wanted privacy and as long as she insisted on going through all my things, I couldn't live with her. She denied all knowledge for a while which was frankly laughable, until she slipped up and mentioned something she could have only known from finding a piece of paper I'd hidden in my room at home. After that She admitted to having been through my room periodically since I was 7.
When DP and I bought our first house together we gave her a key for emergencies. We came home early one day to find her going through our bedroom 
.. she'd also been through our fridge, kitchen cupboards and living room drawers and also gone down into DP's man den in the cellar and been through his computer looking for porn 
DP was the angriest I've ever seen him. He's a really placid guy but he was completely furious. I was too but because I'd dealt with that my whole life it was kind of "normal" 
Needless to say, her key was revoked and it took a very long time for our relationship to recover. I eventually sat her down and explained to her how much it had hurt me and DP. She wasn't sorry and tried to blame us saying we never tell her things about our lives so she "had" to go looking for information . It was then I realized this is compulsive behavior from her and she actually can't help herself. She's lost her relationship with both her daughters as a result of it and it's only now I'm starting to talk to her properly again. My sister still can't speak to her.
She'll never change and I figure she's been punished enough through the loss of any bond with her kids, so I don't mention it anymore. I frankly don't care what she found while she was in our house or while I lived at home, I have nothing to feel guilty about and even if she found something she didn't like, that's entirely her problem not mine.
Remember you're an adult now and the behavior your Mum has shown is the behavior of a child. Don't stoop to that level, pull on your big girl pants and tell her how it made you feel very calmly. If she goes on about how you shouldnt have that stuff or you should have told her about your sexuality, ignore. She's deflecting because she feels guilty. Once you've told her how hurt you are, drop it and walk away. Don't get drawn into an argument, there's no point!
Chin up chuck 