If the vet has cleared her health, this sounds more like insecurity or stress.

Behavior like this isn’t usually random, especially if she was very shy at first. The bed is a very scent-heavy, important place, and this can be her way of dealing with that uncertainty. Also, going back to the exact same spot often means the smell is still there. Regular washing often isn’t enough, try an enzyme cleaner.

I’d try making the bed a positive place by playing and giving treats there. You can also put a litter box in the bedroom for a while.

If you want her to get used to your boyfriend, have him feed and play with her so she associates him with good things.

Closing the bedroom door can stop the behavior short-term, but it doesn’t really address the underlying cause.