Tenant caused mold from leaving unit humid, who pays?

[Zach Nelson]

I have a tenant who lives in a walk-out basement unit in central IL.  She rarely runs her heat and hasn't used the A/C once in the two years she's lived there since being sunken into the earth keeps the unit fairly comfortable.  The major drawback to this is it stays very humid during the summers down there, also due to it being a basement unit.  I verbally warned her when she moved in to make sure she ran the A/C periodically to keep it dry, but she hasn't, and recently she found mold on a lot of her shoes and clothing.  I paid to have a mold inspector come out and while the spread of the mold wasn't severe, their proposed remediation is $2,000.  

The other catch is she is moving out in a month.

How do I handle this?  Do I bill the inspection fee ($200) and the remediation to the tenant?  She tried to run the A/C for the first time now after the inspection and all the refrigerant has leaked out (it was working when she moved in, not sure if it failed from sitting dormant), so that's also going to require a $2000-4000 repair after we find the leak.

Any advice is appreciated!