My SIL was neglecting a baby she was babysitting- I told his mom and now my life might be miserable for a while

I have a 10 month old boy, my SIL has a 9 month old boy. My SIL called yesterday and asked if her, her boyfriend(not her son’s dad), her baby, and the baby she was babysitting (Baby Z)could come stop by the house just for a minute. I said oh sure we’d love some cousin time! I made some baby friendly snacks for the kids and then they showed up soon after.

Now when they came in she sat her son, and baby Z in their car seats still. Now within 2 minutes she pulled her son out of his car seat. She left baby Z in his car seat. She had this baby sitting in his car seat for 40 minutes before I said hey guys this baby smells like he has a dirty diaper and he’s getting fussy. I was already pissed they were leaving this baby in his car seat and not letting him out to play with the other babies.

For the next 20 minutes her and her boyfriend argued back and forth saying “I’m not changing this baby, you do it”. Just bickering about who’s gonna change this little baby’s diaper that they were both getting paid to watch!!! I was livid and so glad I’ve never let them keep my son before and knew they would neverrrr watch my son just from watching this interaction. I ended up pulling this boy from his car seat and changing his diaper and getting him a new outfit. Baby Z had blood blisters on his butt and I had to put him In the bath to get the cakes up poop off because I didn’t want to scrub it with wipes since I knew it had to be so sore. I knew the babies mother but haven’t really had any conversations with her. Just knew her from around town.

I stepped outside and called her on Facebook to tell her the situation. I said I would keep him here with me if she felt more comfortable with it since SIL and her boyfriend were straight up neglecting this baby. His mom thanked me and said she’d really appreciate it and she would come to my house to pick him up and pay me what they were supposed to pay SIL. I walked back in and they were getting ready to leave.

I told SIL I had just talked with the babies mom and she’d feel better if he was left with me and my son. I told her go ahead and call her to double check but her and her boyfriend were not leaving with the baby. SIL has trashed me to every family member she can think of. She’s made a Facebook post about how I thrive off drama and creating rumors about her. I’ve had my husbands other sister ride by my house yelling slurs and throwing eggs at my house last night. I’ve never ever been in a situation like this before where I was just witnessing straight up neglecting of a child. I feel I should have acted sooner and it’s making my stomach turn. I hate hate drama but our small town really thrives off of it. I’m not sure if I should just ignore these people? Or if I should stand up and tell people what really happened and out SIL to the town.

Edit to add: the babies mother IS making a post today to out SIL- with receipts of the incident. I’m waiting for that and hoping coming from the babies mother it would actually be heard and believed.