Cracked bath tub due to tenant

[Mona V.]

My tenant informed me that she slipped, fell and caused a big crack in the fiberglass tub with the knee. House is 13 years old, so I would put life of tub at 13. She is claiming it's bad installation etc because they don't see any support below the tub. From reading through some posts looks like fiberglass tubs are installed like that. Besides builder built what he did. It's damaged caused by tenant and lease says damage should be incurred by tenant in such cases, so I want tenant to be liable for it. I am feeling resistance to it since she already told me her renter insurance doesn't cover it and I should file with mine. 

- Are landlords legally liable for this even if it's clearly caused by tenant accidently, and given age of the tub? 

- What would be my best bet to repair it - I see some miracle repair stuff online, or better option is to replace the tub which could be costlier. 

Thanks!