Landlord won't return deposit

It's the end of my lease yesterday (3 tenants lived in an apartment). I went to return the key and get my deposit back, but the landlady said the new tenant called her saying the bathtub and fridge were messy. a couple of stuff the new tenant bought from one of my former roommates were missing (That roommate did not tell us about her selling stuff, and she had moved out 2 weeks ago). The landlady said she can only return my deposit after this was settled.

I think this is none of my business. What can I do?