My wife posted this in another thread but didn't check the rules and got perma banned just reposting here.

AITAH for expecting my sister to allow my mom to see my daughter on her birthday

So a little bit of backstory on my family.. we are all extremely close and see each other weekly if not more often and always do stuff together. But me and my sister have never been really close, I've just always felt like she wasn't a very genuine person. We always make huge deals out of birthdays for adults and now that I have kids we do for the kids as well usually a family dinner on an off weekend so everybody can make it. I am one of six siblings. Besides a brother who lives out of state I am the only one married with kids. Everyone else either lives with my parents or on their property (all over the ages of 21)

My sister (27 F) has a long history of being an attention seeker. She needs a lot of validation. She recently broke up with her fiance who had a child and that's why she's living with my parents rent free. I myself have 3 kids that are very very close with my entire family my mom in particular. While she was dating her now ex fiancée there was a long history of telling my mom she couldn't go on trips to the zoo, or waterpark with my kids while "hers" was at her bio moms house. While I always was annoyed that my kids were missing out with time with there grandma because of her jealousy, I'm pretty non confrontational and tried brushing it off as caring for the step kids feelings. A couple of my siblings made comments that she is jealous of my family jokingly because they were annoyed by this as well. Sometimes my mom just came anyway and didn't tell her.

Flash forward to about 2weeks ago it's my daughters birthday. Like I said we always have a birthday dinner on the weekend but in the past my mom has asked if she could see the kids for their birthdays and done things with us some times just breakfast other times going to the waterpark depending on what me and my husband have planned for the day. My moms had a lot going on and we were sick the week prior so we hadn't really discussed anything this time. Last minute my daughter said all she wanted to do on her birthday was go to the trampoline park with "Grammy". My brother happened to be coming from out of state last minute as well and my mom had been stressed about having his step kids staying with them as they are a bit crazy and this was the type of thing we would often all do when he visited in the past. The Sunday before my daughters birthday I asked if I paid for her (my mom is on a fixed income) if she would want to come and my brother and his kids could come as well and get out of the house. They would just have to pay for themselves. My sister happened to be sitting behind me when I asked and I watched my moms face drop. She looks at my sister and says "I didn't forget". She said I'm sorry I forgot I committed to voting for your sister in this chilli cook off fundraiser she has for work on Tuesday. My sister does know my daughters birthday and my mom, I just assumed it got overlooked and it was a mistake she planned it on that day. We had family on my husbands side that would love to go with her no big deal (although I did feel bad for my 3 year old that the only person she actually wanted to go couldn't) On the way home from my parents house my husband who didn't know any of this was going on asked what the death glare from my sister to my mom was about. Turns out behind my back she was glaring at her like she better not go. I get she already committed but now I'm a little annoyed that instead of letting the 3 year old have her grandma at her birthday she forced her to go to a chilli cook off for her work. (She's a 28 she would understand her missing out more than a 3 year old would ). Honestly even if she told my mom to go I probably would have said don't worry about it my daughter will be fine. it was more the principle that the thought of my mom seeing my daughter instead disgusted her so much that was bothering me.

My mom text me later apologizing again that if she didn't commit a few weeks ago she would be there and how bad she felt. I told her don't worry my sister in law kept her schedule clear for that day incase we wanted to do something with her kids she already agreed to go. Because of her text I assumed my mom was also annoyed that she wouldn't at least offered to let her go. My 3 year old cried a little when she found out my mom wasn't coming but ultimately had a great time with her cousins. My sister sent pictures of her with a group of coworkers all their chili and bragged how everyone loved her chilli the most and she won. At this point I'm kinda annoyed that it didn't really seem like my mom needed to be there and her presence was more needed with the 3year old. I decide my sister probably doesn't need to be around me or my daughter for a while if she felt everyone going to that was more important than her nieces birthday and I needed time to cool off. I didn't expect her to go and don't really expect anyone to show up for my kids but me, but in our family we always have. I've always made sure to got to her step daughters events when my sister was with her ex fiancée

Anyways fast forward a few days my mom asked if I didn't want to come see my brother before he left since we hadn't came around. I tried to make a few excuses as not to start drama because I needed some space then was going to let it blow over. My mom kept pushing why I wouldn't want to see him. Finally I just came out and text her >quoted text please delete this but I really rather not see ___ and she lives there. I don't feel she should have given a dirty look when you were invited to the birthday and should have let you make your own decision." My mom defended her that she didn't do that and how could I even think she was capable of that. The only reason she didn't come was because she couldn't afford it and a couple other excuses that didn't make sense. She begged I come over to see my brother and not cause trouble. I reluctantly agreed. Obviously my mom told her what happened because the second we walked in she told my daughter happy birthday my daughter sadly said >quoted text my birthdays over" she said well your mom needs to teach you not everything should be on your birthday. This annoyed me so While we were there I held my daughter kind of close and in a way that wasn't obvious to my daughter (I didn't want her involved in the drama that her aunt would do that) I would come up with excuses to call her away if she got close like come pick up your toys, it's time to potty etc. So then she turns her attention to my baby that my brother was holding and grabs her and starts telling the baby how she's a great aunt. I didn't feel comfortable so I went and took the baby and went to leave. My sister started crying that "I was mad that she had to work on my daughters birthday" and my mom went off on me that I was out of line for inviting everyone to a place so expensive. And now my whole family is mad at me for "being mad at my mom for not coming" I tried to say I was only upset that a dirty look was given at the mention of my daughters birthday, but some reason no one accepts that. I even asked if she offered after I left maybe to make sure I wasn't making assumptions (she didn't). So now I'm wondering maybe I was out of line they are my kids not my sisters so AITAH for expecting her to have offered my mom to come if she wanted?