G is an orphan and has no support system or anyone to stand by her. She is uneducated and has a kid to take care of. Its a fact that she did all the housework but she had no choice if she wanted to be near her kid who was her only hope of living. She stayed with Rat only for her kid's sake so that he would not grow up to be like his father and she could play her role in giving him good values. She did try to escape in spite of that after knowing that her kid would be taken away from her by those monsters but was caught in the bargain.
What Padma did today, she would not have been able to if Rat and his gang were around. There is very little that anyone can do (regardless of a male or female) if they were to face a gang of people single handed. Padma, has a brother who is a police inspector hence she has someone to turn to and that too someone with authority. Hence its easier for her to speak up or take the step she took.
About what Sachi told G: Well Sachi said it in very bad taste and she only means to harm G. So I would take it with a pinch of salt. Nevertheless from G's perspective, as long as Sumi was not so vocal and insulting towards G it was totally fine for her to stay at the haveli given that the Singhs forced her to stay and promised to protect her. But with time and with Sachi's entry, things started getting worse with G. She was ridiculed, insulted and treated badly. In such a situation, yes I too hoped she just left the house. Nevertheless, its easier said than done. Not being in a position yet to fend for herself and the responsibility of a kid is not easy for her to take such a drastic step. In this situation, I hoped the Singhs and G could have thought of an alternative accommodation like living in a woman's shelter along with seeking police protection. Things would not have aggravated to such an extent then.