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I'm sorry to hear what you are going through!

Do you think that you can maybe set up a meeting with your aunt and your therapist, if that's something you're comfortable with? It would almost be like a "family meeting" where you are able to tell your aunt what's bugging you in a safe environment where it can be mediated by your therapist. It will also help you set some healthy boundaries with your aunt.

If you feel comfortable talking to your aunt you can do so in a way that isn't rude as well. You can let her know that you love her and appreciate her letting you stay over there to get work done, but there are some things that are concerning to you. Use "I feel" statements, like "I feel uncomfortable when I'm walked in on in the shower," instead of something like "You invaded my privacy," because "you statements" make people more defensive while "I statements" make people more receptive. It can help if you outline what you want to say to your aunt before you talk to her, so you have an idea of what you want to tell her.

Or, you can try and tell your mom, maybe over text so your aunt doesn't overhear. Your mom may be able to talk to your aunt and set some boundaries with her.