AITA for having my daughter’s birthday party on the actual day?

My daughter is turning one in a few weeks, and her birthday happens to fall on a Wednesday. All of my friends and family can also make it on Wednesday, and it was also important for me to have in on her real birthday because one of my best friends is leaving town the next day and really wanted to come. Everyone can make it…except for my sister. My sister is my very best friend, and we talk every day, but I’ll be honest and say she’s incredibly flaky. She lives about 3 hours away, and has 2 children, one of which gets severely carsick and gets physically ill very quickly due to it. I obviously invited her to the party, but I didn’t think she would ACTUALLY come. Last night we were talking about the party, and she realized that the kids are in school (she thought my daughter’s birthday was during Thanksgiving break, but it’s not) and was upset that I was having the party on Wednesday.

I gave her some space, and text her earlier today apologizing for the date of the party. She is obviously hurt, because she said I was accommodating my friend who is going out of town over her. That’s not really the case, and I told her in the nicest way I could that I didn’t think she would actually be attending because every time I had asked her how she would be getting here, she changed the subject or avoided me completely about it. I’ve already sent out invites to everyone with the current date of Wednesday, but should I change the party to happen on Saturday instead? I would feel bad because my friend who’s leaving town the following day has helped a lot, and has gone out of her way a lot for us, so I really wanted her here for the party. AITA for not wanting to change the date of the party to accommodate my sister, who might not even come?

TLDR: My very flaky sister is upset with me for having my daughter’s first birthday party on a day of the week she cannot attend, and I’m not sure if I want to change the date of the party.