Rant!!

My mom and my sister was supposed to buy the baby stroller together since my mom isn't very financially good right now my sister was supposed to go half and half on it... My mom just told me yesterday that she will have to buy the stroller alone because now my sister is complaining that why do I need a car seat if I don't use my car and can't I just borrow a stroller from someone else... I am frustrated because I know my mom is down about this all she wants to get it so I can open it at my baby shower next week but it looks like that won't happen... Idk how to feel about it all.. I will most likely just go half and half with my mom to get the stroller since I know she really wants to get that for me.. I just thought with my sister being a first time aunt she would want to do these things but I guess I was wrong.. What should I do??