Am I just overreacting?

I need to know. Am I overreacting or being petty or something? Or is it okay that I’m starting to get pissed off?

My brother-in-law has been with his wife (I’ll give initials EJ) for just over two years, one year married. Since she’s still fairly new to the family we don’t know her super well. If they’re invited to events, it’s usually just my brother-in-law who shows up and for family/holiday dinners we rarely see them because she makes them go to hers and only hers unless my husband’s family does theirs on a completely different week. Not sure if this is super important, but I want to know if it could factor in to me just being flat out petty or overreacting and creating an issue when there’s none.

Anyway. She’s always been extremely bossy, always has to one up you and tries to turn everything into a competition. I’m sorry, but I hate being in a constant competition that I didn’t ask to be in or sign up for so I often ignore her and her comments when she is around.

Two months ago she had her first child. Her and her husband came over when the baby was about 6 weeks old for a little visit and for my two sons (1 & 2) to meet their new cousin. Weird things happened but I chose to overlook it and chalk up to me over analyzing stuff. A week from there we were all over at my husband’s parents’ for thanksgiving weekend. Now this is where I started to get pissed off at her and not just annoyed. At first, my 2 year old was playing with bubble wrap that was given to him by his grandma. As he’s walking over it EJ decides that he can’t play with it because he’s in the way. Thank goodness my mother-in-law heard, because she stuck up for my son saying she placed it there and he’s fine where he is.

Next incident. My sister-in-law brings down the guitar that my son always plays with when we visit and he sits on the bubble wrap to play with the guitar. All of a sudden there’s EJ yelling from the dining room table “Nuh uh. You can play with one thing, but you have to put one away. You’re not allowed to play with both. Pick the bubble wrap or the guitar” I kindly said back off in nicer words.

The one that really pissed me off. I’m sitting on the end of the couch and my son was at the other end. He pinched his finger in a toy and started crying. He started making his way towards me and lo and behold, someone decides to butt her big mouth in. “Oh, no. Couches are not for standing on. You need to sit down or get off. If you need something you can come see me”

IM SORRY BUT WHAT THE ACTUAL FUCK.

It took everything in me to hold back from telling her off right then and there. Which is why I need help. I need to know if I’m overreacting or if this would piss other people off too? Was I being too nice in holding back since it was a nice gathering with everyone that doesn’t happen often? And how do I even go about this in the future. We don’t see them often, but often enough where it’s going to be a problem if she doesn’t back off and I don’t want to ruin any relationships between my husband and I and his brother and wife.