If she truly is the new owner, she certainly is extremely unprofessional.
As for the deposit, yes, she is liable for that too. If you had to take her to small claims the judge would tell her to pay you and then her next step would be to sue the other person who skipped with the deposits. That problem is certainly not your problem.
I wouldn't sign anything without real proof that she is the owner and I absolutely would not sign anything saying you did not give a deposit.