You can write up an amendment to the contract and get an extension.

She will avoid an eviction on her record, not incur further costs, and might prompt her to stay in the hospital longer.We recently amended our emergency contact form to include a section of the form where the tenant gives permission to a person they name to remove their belongings from the apartment "in the event of their unanticipated prolonged absence from the apartment".  

You NEVER leave anything to chance...send an amendment of the contract of have the wholeselller rewrite it with the stipulation you want in there IN PLAIN ENGLISH.

This elevated his concerns and was a bit more amendable.

Then I would amend the rental agreement to put more responsibility onto the tenant for maintaining it that way and for notifying me in a timely manner if a re-infestation occurs.

I give everyone a pass now and again, but when they don't meet the amended expectation after you have made a change or allowed an allowance on their behalf, follow through 100% with what is needed.  

Are there any creative ways to amend this agreement?

If you can get the listing agent to agree to what would be an amendment to the contract, that would be the best case scenario.

An agent can fill in the blanks on an approved form, but only a lawyer can write and amend contracts.

Make sure that all changes are known to both parties and amend the inspection period and the closing period....