Tenant moving out

[Devon Curney]

I'm still new to real estate and I would appreciate any advice I could get.  My mother just bought a duplex last year in Chicago with a tenant already living there.  The tenant told her she was moving and will live out her next two months with her security deposit. We don't know what to do in this situation. The old landlord never gave her the security deposit we don't know if she even gave him the deposit.  What should my mother do take her to court or just let her leave?  What should the next action be? Thanks in advance.