sna
If you can show evidence that you gave notice ending the tenancy, then you will almost certainly not be held liable. Make sure you go to court and bring this to their attention. It will likely cause the entire case be thrown out.
However, even if you win, being named in an “unlawful detainer” suit may hamper future housing applications. I would tell the property manager you are prepared to file an action against them for defamation and malicious prosecution. Even better if you can get a lawyer to spend an hour drafting this message in a letter sent to the prop manager and landlord.
The mistake here was that the property manager didn’t create a new lease agreement when you gave notice. They should have. If you haven’t called the landlord, you should and tell him/her what is happening.
p.s. — not a lawyer, so take what I saw with a grain of salt.