Louis gave you great advise, if your mothers landlord is not providing heat (or working heating system) you may also withhold rent. Keep in mind when you withhold rent you should put it in a separate account and make it available to the landlord as soon as the issue is fixed. Your mother may qualify for free legal assistance, many people use Community Legal Aid http://www.communitylegal.org
Scott is overstepping his bounds and mis-informing you as what to do.
Although your mother is elderly that has nothing to do with what is required under the housing laws in Massachusetts as to heat. You may want to visit this web site and see if the heat within the property meets the law.
If they are not being meet then I suggest you send a certified letter to the landlord and contact the local health department and the attorney generals office.
If you need guidance there are many free legal aid services available within the community
Hope that helps,