Mom Invades my Privacy, and I’m an Adult

So, I recently turned 18, but still can’t think of a way to talk to my mom about an issue I’ve had with her for several years now. I do still live in her house, but I’m still a person, and I’m about to move out soon anyways for University.

I have a very large family, so anytime I have to myself is very precious to me. My mother doesn’t seem to understand this, however, and tends to walk in on me whenever she pleases. She walks in on me in both my room and the bathroom when she feels that I’ve been taking too long for whatever. She routinely walks in on me while I am showering as well. It makes me feel weird considering I’m no longer a child, even if she is my mom. She has walked in on me naked and won’t leave until she’s done saying her piece, even if I yell at her. All of the bathroom and bedroom doors even have locks, but she’ll unlock them knowing I’m inside.

My mom and I are very close, and I feel like I can come to her about literally anything else but this. I just don’t want her to get mad and go on the whole “my house, my rules” tirade again. I feel very helpless when it comes to this topic, and I don’t want to leave home thinking “Thank god,” to myself. I want to leave home with an open air and mutual respect between us. Any advice anyone could give me? I’d really appreciate it.