We had briefly considered trying to see if the home could be repaired and have mold remediation to rent it out, but the neighborhood has gone down in quality over the years and we are hesitant to have responsibility over upkeep of the home.

If the breach is not remedied within the five(5) days, the rental agreement shall terminate as provided in thenotice subject to the following: If the breach is remediable byrepairs or the payment of damages or otherwise and the tenantadequately remedies the breach before the date specified in thenotice, the rental agreement shall not terminate.

I would give her the standard grace period (whatever is dictated by lease) and then let her know that she is late and you will pursue whatever remedies you have at your disposal. 

- What steps should I take right now to remedy the situation?

Remediation is largely to protect you from liability. 

A good local Realtor can help you with that.The advise that @Bjorn Ahlblad gave you above is categorically wrong and depending on state law, can land you in a world of hurt.For example, I can tell you with 100% certainty that in Massachusetts (I'm also licensed there), if there is a child 6 or younger living in the home, the owner MUST test for and remediate lead paint.  

Any ideas on remedy?

I have not done this specifically, but have had asbestos remediation training so am familiar with the issues. 

Once the seller understood that the remedy for us was for the seller to be forced to turn the property over under Specific Performance, but also cover all attorney’s fees and court costs, they begrudgingly moved forward.

So are 3 bed rental was apparently used as a meth lab and now requires remediation...which consists of complete cleaning and replacement of exhaust vents and cleaning furnace.