Can't even change clothes in private at home?

I have a bit of an issue that I don’t know how to solve. I currently live with my grandparents and have my own room. If my grandmother needs me, she CONSTANTLY just opens the door to talk to me. No knocking at all. She did it today because she had a question and I asked her politely if she could start knocking before just walking in because I was in the middle of getting ready for work! While luckily enough I was putting on my makeup and not changing my clothes, I easily could have been. Sometimes I put on makeup when I’m in my underwear, walk around looking for clothes/underwear while naked, etc. Because I should expect that kind of privacy right? I don’t change clothes in the bathroom because I have to share it with her and I take a long time to get ready. She always complains in the morning when she has to use it too, so I’ve started to take my baths/showers at night and only spend my mornings in the bathroom to wash my face and brush my teeth so she can have “her” space.

Anyway, she got mad that I asked her to start knocking. Her words were “I can’t deal with all of these ‘privacy’ rules. What do you mean you could’ve been naked? You’re not though? I’ve seen you before you’ve seen yourself!”

I’m TWENTY ONE YEARS OLD. Privacy rules?! I think asking someone to knock before they come in when I have my door closed is pretty reasonable. More than once has she tried to barge into my room while I was actually undressed and I’ve had to hide behind the door, frantically push the door back closed, or quickly cover myself, etc. I don’t know what to do to make her stop :( Locked doors are already against the rules “in case of emergency” and all that