Need some ideas to get annoy a dramatic flatmate?

Okay, so there is this polish girl in my flat which we can call her "A". At the beginning of the semester, we were friends, going out all the time. Then she kept using my dishes and not washing them- just leaving a mess everywhere. I just was cleaning my dishes that she used. She then was doing it so much that i felt like she was taking the piss. I did tell everyone at the start of the semester that they can use my stuff as long as they wash it. I then saw her use my cups then she put soap in it and filled it up with water and just left them in the sink like that. she continued to wash all her other dishes as normal and put them to dry. I didn't say anything but i just washed it. I think i am a friendly flatmate, i always share, like once everyone was chilling in the kitchen and we had a guest over (one flatmate's friend). he was very hungry so i thought i would give him a packet of crisps and then i thought i might as well give everyone else one, A took two but i don't mind. When we went out clubbing, A was tipsy and she has a job and i don't, she clearly had money as she was coming from a rich family as well. she asked me to buy her a drink though even though she had her card with her, i just bought her one and she said she'll pay me back, which she never did but i never mentioned it to her. I used to say hi and bye to A in the kitchen and she would just completely ignore me. Then once, i just got fed up of washing her things as well so i put post-it-notes into my cupboards saying that no one can use my dishes anymore. a few days later, i saw that someone had taken some stuff from my cupboard and used it but didn't wash it. i was obviously annoyed so i messaged on the group chat saying that i have put up post it notes to make everyone aware, and that whoever used it if they could clean it up please. A started laughing on the groupchat. a few minutes later i went into the kitchen to wash up and A was in there. I was just using the soap that was by the sink ( i thought the cleaners put it there). She came up to me and said "oh, that is my soap, you can't use it because only those who contribute as part of a family and share their things can use it. as we are all meant to act like a family and if someone is not going to contribute then they can't be part of some things or use some things " i was so annoyed with her and told her "well i did let everyone use my things and share things at first but if people are going to not wash up then i have to do that". the way she was saying it to me was really rude.

After, when we see each other in the kitchen, i don't even make effort to say hi or bye to her anymore and she doesn't either. she used my things the other day and i asked her, but she lied about it, she said it was her stuff when it wasn't. i started to say hi and bye again in the kitchen but she would air me, so when she started doing it, i had to as well. she would normally make sarcastic comments mainly aimed at me when we are all together. i think she told her friend something about me because now her friend is ignoring me. i don't understand what i have done wrong and what's her problem with me. i still let everyone use my sponge and brush as the flat one has broken. she said i "lock away" all my dishes when they are still in the kitchen. even though others keep theirs in their room and she no problem with that. i was on facetime with my boyfriend and she was trying to make as much noise as possible in the kitchen. she is just a child.

I want to annoy her, just a bit. so that she knows not to mess with me and she'll stop. i have tried talking to her about it, but she does things more when i tell her to stop. i want something where i can do stuff in the kitchen like a prank or something but i don't know what.

This whole issue could go away if you kept your things in your room. You were nice at first to let people borrow your things, but when they didn't clean them, the logical thing to do is move your things into your room where she can't get to them. Keep your room locked when you're not home. The uni year is almost over anyway so imo it's not worth trying to annoy her or do anything.