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Dear what can I do?
Without the cooperation of your daughter's mother and the landlord you remain the tenant. You do not want to be responsible for making your child homeless and by this lease, you are providing a home as long as the lease is in effect and the rent is paid.
The answer provided to you is in the nature of general information. The general proposition being that you should try to avoid a bad outcome if you can.
I don't believe there is much you can do but convince your girlfriend to move. Or make sure she is paying the rent. You do want to keep a roof over your daughters head so you may have to just deal with this.
This is something that should be addressed to get you the best result possible. I think you should meet with an attorney in person.