When my parents-in-law decided to pay down payment for a house as soon as we got married, one condition was to have my husband's younger sister (one year apart) on the title and live with us. I was not happy with the condition and got into countless fights with my husband because he did not see anything wrong with living with his sister when we got married but due to financial reasons, I accepted it. It's been three years and today my husband finally asked his mom what we should do. My mother-in-law called her daughter and asked when she was going to move out. My sister-in-law got very upset and started yelling/crying at my husband for talking to her mom about the living situation. I'm very upset that she does not feel bad at all about the situation and even worse she blamed us for everything.
To make the matter worse, my mother-in-law suggested that we pay half of the down payment amount she helped us with to my sister-in-law so she could move out. We don't have enough money to pay her out like that and I honestly don't understand why it's our responsiblity to pay her out.
I see everything wrong with the situation but I need advice on how I deal with this situation.
What can I do?