[Landlord-US-CT] Tenant Demanding Money Back After Changing Mind During Move-In

The tenant gave a portion of their security deposit, $200 of $650, two weeks before moving in. I said they can send the rest once moving in. No contract/lease was signed. Room was taken off market for those two weeks. Then, tenant changed their mind. As the apartment owner (lease under my name, I’m renting a room), am I obligated to give them back their deposit portion? I incurred $325 in losses due to taking it off the market. They are now threatening to sue for those $200. This transpired in March 2025. Thank you!