How do you know if your getting scammed from someone from Lagos, Nigeria?

I have been talking to a woman that is said to be from the State I am from. I feel bad because she said that she was over there taking care of her mom that was taken their, but her boyfriend and left. She tells me they are starving and need food and meds. They don't have no one to help them. I have sent money but I feel like I am being taken. I know it has been 4 weeks and I have not sent any money for food or meds, but she is still alive and gets on the computer every once and a wail. It is hard to believe that she is still alive after all this time, with out eating for 4 weeks. But maybe she really does need my help. I don't know what to do? Please help me find out what I should do?