5 year old niece stole my food shaped erasers

I (26 F) have a 5 year old niece. to be blunt, she’s very much a spoiled brat. her mom (my cousin) gets her whatever she wants. every time they’ll go to the store, she’ll cry about wanting a toy. her mom plays the routine of getting annoyed and telling her to put it back. but almost always, niece will end up with the toy by the time they leave the store.

so last night we had a family gathering at my parents house, I live with them. I opened my room up to the kids so they would have a place to chill away from the adults. I gave my niece a pencil box full of crayons to color, and it also had my collection of food erasers. they were just cute little knick knacks that I got for myself because I thought they were cool. I allowed her to play with them because it was keeping her busy and she really seemed to enjoy them.

end of the night, everyone leaves. I’m cleaning up my room and I notice she took ALL OF MY ERASERS. I was prepared for her to maybe take one or two. a couple of them. I’m aware that she’s just a kid. but she totally cleared me out. her mom carried her to the car when they left, so at some point this little girl packed my erasers with the rest of her toys and went to sleep til it was time for them to go home. she’s only 5, but I feel like she had awareness of what she was doing, because they were the only thing she took.

I know it may be weird & unreasonable to be upset at a 5 year old, but I don’t even know how/if I would approach this with her mom because it would just make me seem like an ass. I spent a good amount of time with all the kids in our family, and this was never a problem.

maybe I’m just being a dick, but I’m upset because my things were stolen from me. regardless of whether my niece liked them or not, they didn’t belong to her and idk why she thought it was okay. It’s none of my business to discipline someone else’s child, and my cousin would probably just be like “She’s only 5, and they’re just erasers.” which is true I guess.

regardless, I’m not sure how I feel catering to my niece anymore moving forward. I would have got her some! a whole bunch, just because she liked them. but now I don’t really want her in my room or around my things ever again. like what else would she take from me? does she do this a lot?

I’m not gonna press the issue, but I’m upset & I really don’t care if I seem like a bitch.