contact your local health dept. to see if they can offer any help

Hydrogen sulfide is toxic but may not be a health hazard.

Similarly, in another experiment, health researchers found that their efforts to get young women to check for breast cancer through self-examination were significantly more successful if they stated their case in terms of what the women stood to lose in terms of health benefits as opposed to what they could gain.

Seems like she will be unwilling, so it is possible you can take her to small claims court and sue for pain and suffering in the form of moving expenses and stress .  

@Clarissa Nesbitt, I feel your pain!

The swimming pool was shut down by the health department.

As far as your original question, I personally would probably keep the townhouse unless it becomes a pain to manage.

You on the other hand feel their pain and would like to offer them assistance in their move by perhaps hiring the moving van, offering them some financial assistance, etc.Nice only works with some people, so if they are going to abuse the system and take you down a long nasty road, your will have no choice but to go down that road.

My investment was not substantial, just paying the property tax to me is making the pain worse.  

I understand the health and safety issues in renting and the town has an interest in protecting tenants and their rights.