Ridiculous?

My sister and I had our baby's around 8 months apart. The issue is she gets SO jealous if any one in the family pays any attention to my LO. It's to the point were whenever we go to vist my mom everyone in the family knows to give hugs and say hi to her daughter first which isn't a big deal to me, I just find it ridiculous. If my mom comments how much she loves my son she'll make a comment like " yea you dont love (her daughters name) as much." My mom can't buy anything for my son or any other of her grandchildren (she has alot of grand kids) without getting something for my sister's daughter as well. There was even a point were my other sisters straight up ignored my child because they didint want to piss her off. He's still a baby but it still really got to me. She also sat there saying people have told her that when her daughter was a baby ( she's a little older now) she was the most gorgeous baby they've ever seen and then looked at me like I should agree. I love my niece and think she's adorable but I'm not gonna say she's any cuter then my son. Am I overreacting on the whole thing or is this as ridiculous as I think?