Getting sued by tenant over bodily injury, What should I do?

I have a couple properties, which several of them are trailers. The tenant did much work to the trailer that was not authorized by me, I stated in the contract not to do any work w/o notifying and permission of landlord. They did some tile work and the female tenant's foot cracked thru the floor. She hurt her foot and got a laywer and is sueing me because of her foot. Also they are 2 weeks late on rent and I served them w/ a 3 day notice. Any advise?