My(22F)best friend(23F)won’t give back my ex’s(25M)clothes and it’s starting to upset me

I (22F) had my best friend (23F) sleep over a couple weeks ago. The next morning, I gave her some clothes to wear as she didn’t have new ones, it was just random stuff I had lying around, including a pair of sweatpants and a t-shirt that used to belong to my ex. We’ve joked before about how I still have a bunch of his stuff (he lived with me for a while, so yeah, some things stuck around).

About a week later, I asked if she could return them. She said she would wash them first, which was fine. But now it’s been another week and she told me she’s not going to give them back. I was honestly confused and asked why. She said it’s for my own good, implying that keeping his stuff around isn’t healthy.

I get the intention. A few months ago, she threw out a pair of his old slippers I had. At the time, I was in a good place and didn’t really care, so I let it go. But this time feels different. I didn’t ask her to get rid of anything, just to return it, and it’s starting to annoy me. I feel disrespected, even if she thinks she’s helping.

How should I handle this without blowing things out of proportion? I don’t want to fight, but I also don’t want to let my boundaries slide.

TL;DR:
I lent my best friend my ex’s clothes to wear, asked for them back, and now she refuses to return them “for my own good.” I understand her reasoning but it’s upsetting me. Not sure how to handle this without causing drama.