What are your opinions on unreported repairs? Do you add anything to the lease to encourage quick reporting? And who is responsible if unrepaired item causes damage to tenant property or rental unit?

Backstory: Renting out a very bright and clean basement apartment with painted concrete walls. High Ohio summer humidity causes condesation on walls if dehumidifier isn't on 24/7. Tenant vaguely mentioned some mild condesation in cold corners of walls, but didnt ask for repairs or mention it again later. Was there to repair unrelated damage and saw water but was less than a hot shower causes in a bathroom. Not realizing the risk as this is a new property, did not follow up. 

Fast forward 3 weeks and she sends a text that there is mold everywhere and she's not sure what to do. We inspect and find a thin line of mildew around the lower perimeter of apartment and thicker in corners. Her mattress, bags, and clothes also have water damage as they were laying on the ground next to concrete walls and tile floor for weeks while the condesation persist. Her vacationing roomates stuff is all safely placed away from wall. 

We get dehumidifier that day, cleaned up walls the day after at her request (plans that night), caulk windows, door, and wall/floor corners, and call plumber for good measure. He says we did it right and can't see any blockage of interior or exterior footer drains to sump pump that could cause seeping. Inspected it every day then every few days and no more water.

However, tenant wants us to pay for damages. We tell her to file with renters insurance, which is strongly encouraged by lease but not required. She doesn't have any and argues that flooding wouldnt be covered anyway. Claims we are liable due to neglence since she told us. We disagree with her interpretation since she never requested repairs and failed to inform us of the severity of issue. However we felt sympathetic and agreed to lower her earlier animal damage bill to offset her loss. 

Have these numbers in email, but didn't get any signed papers declaring the matter closed. The exchange of money is complete but she's still upset. Revisits the topic occasionally and passively implies that we are sleazy and she is victim. 

Overall she's been a okay tenant and rent has always cleared. But seeing red flags now and feel business relationships is damaged.  Also a frustrated  because her lack of communication could have done damage to my investment. Have offered to reassign her lease if she wanted to move out, but she hasn't taken the offer. Wondering if we should have handled it differently or preemtively add something to the lease next year.  Also, are we liable at all? See court cases where LL are successful sued for not providing adequate security or failing to provide a habitable living environment. Advice appreciated.