I am sorry she is giving you a hard time. It is straight from the playbook, though. Every. Single. Time.
That is why I
don't charge a deposit. No issues when they leave. 99% of the time they leave the day I give notice so I simply have them pay Monday mornings in advance for the week. If they leave Friday, I lost nothing. If they leave Wednesday, they lose two days stay.
I hope your next client is golden, you deserve it.