So, the tenancy is in joint names, so you have a joint responsibility for returning it in a decent state at the end. That’s fair enough.
I’m presuming she has paid the most recent rent? If so, she is entitled to keep things there. I’m going to suggest she also has every right of access to the property as she sees fit, unless you have reason to believe you are at risk and go to the Police.
The rabbits are not your problem, though. If she is planning to leave them with you, make it clear that you’ll simply report them as abandoned to the RSPCA.
It’s only a month. She will be out of your life soon enough.
Rachel