This indeed is a knotty problem. The woman has to put a lot of things into consideration while looking at the problem from a multi dimensional angle ie, could it be a spiritual thing, or just the polygamous nature of man or maybe pressure from his family( knowing the African mentality).
If its a spiritual problem, she has to go to God in serious prayers and wait on God to fight her battles.
On the other hand, if it is societal influence, in as much as we are called to be submissive, she should not give in to this form of abuse all in the name of marriage. If she gives him a step, he will take a mile and someday she and her daughter will literally become their slave. wat is marriage when there is no mutual love and respect? her love for her husband should not make her destroy her pride as a mother and the role model to her daughter. Her action will have a lasting effect on the daughter.
I'll strongly suggest she doesn't go on her kneels for any woman. The worst that can happen is divorce(I'm not an advocate for divorce but its better than slavery)she wil have custody of her child. By God's grace she will be able to take care of her and who knows some day, the man might come back to her and even if he doesn't, she might find happiness else where.