Her husband is a loser, okay, does she divorce him? No, she cheats on him, nothing like kicking a guy when he's down! How is that sympathetic?
I just don't see any likable characters here. We have a loser husband who sits around in bars drinking with no regard to his family, including a little girl, we have the mother who cheats on her deadbeat husband with two guys, guys he knows and were rivals of his, and we have a conniving mother who sees no redeeming value in her own son and literary plots his total humiliation and degradation. I sure hope the little girl is likable.
It's just not my kind of story, doesn't mean a lot of people won't like it.
Well, the mother's actions are initially altruistic and praiseworthy since she wants to make enough money to provide the best for her family's welfare. The same applies to her mother-in-law who also feels sorry for her son's wife. But as you say, each to his own.