It really depends on the location and price of this house.
the benefits system is there to support the needy, not property owners, so its unlikely she will be successful. I think the Benefits system will not allow someone who owns property and has a mortgage to get Housing Benefit. She could ask her estranged husband to take her off the mortgage, he would be probably more than happy to do that. Once clear of a Mortgage I would suggest she sells the house with the other owner and with the capital either support herself and her family, get full time job and apply for a small mortage with low LTV, or buy a cheaper house for cash. It really depends on the location and price of this house.
The benefits system is there to support the needy, not property owners, so its unlikely she will be successful.