Her mother is enstranged from the rest of the extended family and doesnt talk to them.
This is a MAJOR
RED FLAG !
Latin families are very close, even when they don't like each other or have mistreated each other. If the rest of the family can't get along with this woman, what makes you think she is a good investment?
If you don't shut this money-sucking siphon off now, it will bleed you indefinitely for years to come.Whether the background story is true or not, to me, is actually irrelevant. The idea of supporting this woman who refuses to even HELP support herself is ridiculous.
However, if you decide to proceed at your own risk...
One of my good gringo friends told his Latina wife that whatever amount she contributed to her family BEFORE she came to the USA, they will continue to send the same amount now that she is in the USA. No more, no less. That sounds fair. That way the Latin family doesn't lose the income, and it doesn't cut too much into the gringo's budget.
NOTE: In the case you've described though, your novia could cause this to spiral out of control. She could start working more hours in the USA just to meet Mommy Dearest's demands for more cash.
In the words of the great economist Biggie Smalls (aka Notorious B-I-G)...
"Mo Money... Mo Problems"