Tenant didn't notify me about bed bugs

[Ross Miller]

A tenant just notified me that she has bed bugs. I checked the lease and realized that I made a major mistake. I check marked the wrong box stating that the landlord pays for bed bug removal. 

While meeting a pest control expert there, the tenants adult daughter said they threw away their mattresses about a month ago. The tenant claims it wasn't that long ago, but actually 2 weeks ago. The pest control guy said the infestation is very bad and looks like it's been going on for a while. 

So at the very least, she knew she had bed bugs and didn't notify me for 2 weeks. I realize I screwed up the lease and likely made myself responsible for paying for the treatment. However, if I had been notified sooner, the pest control guy said I could have used a cheaper conventional removal at a cost of $630. Now though, he said he would highly recommend the more thorough heat treatment method at a cost of  $1250. 

Would it be unreasonable or illegal to charge my tenant the difference between the two treatments since she didn't notify me?

Also, this tenant has been problematic for a while now. She is on a month to month lease. If I don't want to renew her lease, can I legally blame it on her not notifying me of a major problem? Do I even need to give a reason?

Thanks for any help.