AITA for telling my wife her expectations for her sister are unrealistic?

My wife 28f and I 29M just had our first child together 4 months ago. It’s been stressful but fulfilling time in our lives together. The only perceived issue has been how involved my wife’s sister P 30F has been with the baby. P to put it simply is not a baby person, she doesn’t want kids but has always been supportive during the pregnancy. My wife thought that she would be around more than she is to help take the burden off of us but she has expressed that having to take care of a baby makes her extremely uncomfortable even just for a couple hours.

The thing is my wife is constantly nagging her to help more everytime she sees her sister, so the little help we do get is gone since P is now avoiding us completely. I told my wife that her expectations are unreasonable given she’s always known how P has felt about kids and she needs to let it go and apologize before we lose P from helping us completely in the future. She’s now giving me the cold shoulder because I’ve picked her sisters side over hers.