Massachusetts . My Dad passed away and left My sister ,Myself and my brother a home with no mortgage . . . .
....What had happened ( not to complicate the issue) we went to the reading of the will and my dad had in his will that my sister could live in the house as long as she could afford the associated costs, but according to my dads attorney he had legally given the house to the 3 of us 5 years earlier than his will which means he didn't have the right to put any conditions on the house because it in actuality wasn't his ? Does this make sense ?
No it does not make a lot of sense when in one breathe to declare that the home was distributed in co-tenancy through probate of a will and in another that the property was deeded inter vivos!
You seem fully aware that either co-tenant can petition for partition that would result in the home being sold. In which case the answer to your specific question of whether or not sister would have legal grounds to object and prevent such is negative. The right of one or more co-owners to force partition is indefensible.
Whether or not sister can qualify to obtain a mortgage loan or whether she is inclined to do so are questions beyond resolution here. But it seems to me that you and your brother are being hesitant just to accommodate her desire to remain in the home. If that attitude of deference continues, nothing will be accomplished.
My advise is that you take a firm line with her letting her know that if the issue is forced she will eventually be compelled to either purchase your interests by means of a mortgage loan or see the home sold at a public auction.