Good. Be the bad guy, so she doesn't have to. That's a bullshit request. Every pregnancy is a risk, and requires physical sacrifice to be made by the mother. Every (good) parent sacrifices time, energy, and various comforts for their child's sake on a frequent basis. If that bitch can't even sacrifice some excess calories (she is clearly demonstrating that food is more important to her than her sister), she does not have the ability to parent, and does not deserve to be one.