need to vent will take advice

Moved in with a family member with my fiancé and 1 year old last year due to family member passing away so she could no longer afford to live there and nobody wanted her to have to find a place and move right away. Well long story short she bosses my daughter around to the point where she won't listen to me unless she's not home or we are not home. I recently have had a baby (2weeks ago) so we expected my daughter now 2 to misbehave a bit as she's no longer an only child well this lady yells at my daughter throughout the day and has threatened to hit her when she doesn't listen. I can't  bring my newborn down stairs or just walk in the house and she attacking me to hold him, even when he is eating (breastfeeding) and complains that I hate her and telling my daughter crap. Like I'm trying to get my family out of this house but me not working for about another month isn't helping as we will need two incomes for our own place.