What would you do in this situation???

I have two sister in laws (SIL). The both of them don’t speak to each other at all for the last 8 years or so ( this was before i joined the family). They both have kids and the kids play with each other just fine when they see each other. From what i have been told, they don’t talk for the dumbest freaking reason but I have stayed neutral since i joined the family 6 year ago. I have never talked about their situation or even had a conversation about it because i don’t want to be involved or have to choose side... Now for the last 2.5 years, the one SIL stopped talking to me randomly which i thought was pretty fucking weird. They live in a different state btw and we see them maybe 2 times a year at my in-laws house since they moved. I would message her, call her on FaceTime to check on them like i normally would and to talk to the kids, invited her to my baby shower etc, she never responds or even acknowledges the messages or calls . She won’t even acknowledge any gifts we buy their kids..Saw her once when i was pregnant with my baby. Not a single word, she ignored my greetings and walked away (in front of my husband and her husband), never said congratulations on pregnancy (considering the fact that she knew we were having fertility issues) or when the baby came or never even said “happy birthday” when he turned 1, few weeks ago. Never acknowledged his existence whatsoever… She doesn’t really talk to my husband anymore either. My brother in law stays neutral in this whole thing and pretty much pretends like he doesn’t know that this is going on… My in-laws also don’t say a word about this whole thing and they are aware that this SIL doesn’t talk to the other two SIL (me included). Now, we are planning to go to my in laws for Christmas Eve. The whole family will be there… i told my husband that i don’t want this SIL anywhere near our child which i think is pretty fair considering all the stuff i have mentioned above. I would not feel comfortable with her carrying our baby. Would you let this SIL touch or carry your child? If you were her husband (my BIL), would you get involved to figure out what’s going on? I truly believe this type of behavior is ruining the relationship with the nieces and nephews. My husband is debating saying something to his brother but doesn’t want any conflict. He doesn’t know how to stop her from touching our baby without making situations worse. Am I being petty for not wanting her anywhere near my baby?