If something is behind the wall it seems to be a small area that would need remediation.

The tenant defaulted so you can pursue whatever remedy is prescribed in your lease agreement. 

Have the home tested during your inspection phase; if lead paint is present, you can always request for it to be remediated or walk away from the deal.

No, it is not an easy fix but why force residents to deal with a bad design in perpetuity that can be remedied within a matter of days and dollars.

Make it clear to her that she is NOT to attempt remedy, just like she was NOT allows to do it in the first place.

As the project progresses, if they aren’t hitting their milestones within the agreed upon schedule, ask them how they are going to accelerate their work and submit to you a recovery schedule to remedy.

As far as I know, saying you will remove the tree means nothing because you were just made aware of the situation and will remedy it.

@Joe Splitrock I guess I wanted to offer some kind of remedy.

When we had a broken water pipe in our concrete foundation slab (will never buy another house on a slab - lesson learned) and the house needed water remediation we discounted our tenant's next monthly rent payment by the amount of the hotel stay after they provided the hotel receipt.

I intend to take the proper steps to have a professional find the source of the mold, test it, and have the mold remediated.