What possible charges can we file against a person who has been taking advantage of the situation?

This woman was my brother's live-in partner for 3 years. Their union gave them a daughter who is now already 3-year old. My brother tried to make their union formal by asking her to marry him but for some reasons, she declined to his proposal. Despite of that they decided to keep their relationship for the sake of their child. I could say that everything was not perfect for them. In fact, each has his own misgivings. My brother being very stingy and her being irresponsible. By the way, they live with my parents. For the whole 3 years that they have been together, there have been several times that the girl would leave to visit her mother and would not return until 1 month, leaving her child to the care of our parents. Her mother was not ill anyway. In fact up to know, we still couldnt figure out what she has been doing all those times that she was away. This scenario continue to happens for several times (in fact she did it more than 10 times during the course of their relationship) until recently my brother could not take it anymore and decided to end their relationship. Him being afraid, that the girl might be doing other things such as having an affair. The reason why he thought so was overhearing her calling somebody baby over the phone and some text messages. To make things worst, my brother met another girl who became his girlfriend. The girl does not live with our parents anymore, in fact she left with my niece and stayed with her mother. My question is, is it right for her to demand some money from my parents? She said its for her baby. But recently her demand for financial support went from monthly to weekly. My intention is not to stop the financial support. By the way, my brother also gives her financial support.I just dont want her to take advantage of my old folks who can't help but worry about their grandchild too much.