Certifiably Crazy Tenant Terminating Lease

Tenant emailed me today with 'intent' to terminate lease and leave the apartment on Monday, 5 months before the lease term (about 8k in potentially owed rent). She is claiming the house in uninhabitable due to an infestation of mice-- rendering our apartment a health and safety concern. She has 4 daughters, 2 of which still live at home. I'd like to know what my options are moving forward. Is it even worth the effort and stress for legal action?

Our tenants are slobs to put it mildly. Food, garbage and clutter are piled in every corner, under every bed-- covering all areas and this is not an exaggeration. (EX: After two visits, 1 month apart, the same pile of food/halloween candy and wrappers remained under a chair.) The mice are thriving due to poor living conditions and clutter as stated by the exterminator. She does not clean the mess, she just complains about it. She does not believe that candy, candy wrappers or food wrappers are garbage.

I below her apartment and while I have seen evidence of mice, the droppings can be counted on my hands. There is no indication of an infestation. I have made every attempt to rectify the situation, sealing gaps/cracks, bringing in exterminators, providing traps, etc. She claims they have moved in and are more like pets than rodents. They have "attacked one of her daughters in her sleep" Her daughter is 19 years old... imagine that? After 19 months of living in my home, her daughter has developed an allergy to pet hair (ironically that daughter doesn't even live there). The problem was also "going on for months" before she brought it to our attention.

She is hostile and lacks the ability to have a conversation face to face so everything is done through email. I am so frustrated and would love to share emails and conversations but the post would be too lengthy!