Ex won’t return my things, I’ve asked 3 times and the 3rd time she blocked me

Hey all. My ex ended things for the final time with me after a very tumultuous on and off relationship for the better part of a year. After she broke up with me, I told her to let me know a time we could coordinate for me to get my things back. I asked a second time, she said we would talk about it at the end of the week when she was off work. She never reached out. I asked a third time, angrily, because she was posting herself doing tons of other things and clearly not making getting my things back a priority when she could have. She called me “selfish and entitled” and explained a lot of personal things were going on I had no way of knowing about. She blocked me and said she would “mail my things back”.

It’s been a week now. I have a feeling she won’t mail my things back and this is a form of punishment. Any advice?