Letter/verbage for not returning a security deposit

[James Smith]

Hey everyone!

We had our tenant send a text message stating she was giving her 30 days on a month to month lease on July 31 asking to live out her security deposit. I let her know that would not be possible and her lease states 60 day notice is required. She argues it's not legally binding and she is only required to give 30 days on a month to month in PA. She threatened legal action and I know I'm in the right there but what/how do I prepare a letter to let her know her security deposit will not be returned because of unpaid rent?