Is OTHER wrong in the post ? POST : I'm gonna apologize for formatting right away, mobile. I'll do my best. 

Anyways, last summer, my family and I found out that my little sister was qualified for a trip from Wishes &amp; More, a company similar to Make-a-wish. My sister has ITP, an immune disorder that makes it so she has a super low platelet count in her blood. This basically means that she bruises easily, and any head trauma is serious. She no longer has active ITP, and her platelet count is normal. However, she has the chance of it dropping again in the future.

We are to go to Disney for her trip, originally we were supposed to go over this past winter break. However, she got sick and so did my other siblings, so we rescheduled. The new dates are over spring break, and the week following. This means I would be missing a week of class, and missing 3 midterms. Not something easy for college classes.

Now since rescheduling, I have moved out and started a new job, one that I've been trying to get for a year. I am 18, and have obligations too. My professors said I can miss the midterms, but they can't have me take them early or late because it runs the risk of cheating. Whatever. Dispite explain things to my mom, she doesn't understand that I am an adult now and I have obligations other than my family. I think it's harder for her there because previously, I worked as a PCA (personal care assistant) for both my sister and my brother, and could help out more than I can now.

I have offered to try and get a plane ticket for part of the trip, as the rest of my family is taking a transit van down, adding 5 extra days of just travel to the trip (we're from Minnesota). I can't really afford to do this, but either way, this isn't a good enough option for her either. 

Anyways, now that I've finally stated officially that I can't go, she is being super passive aggressive and mean every time I reach out. Even if I'm trying to help her in other ways, like offer to watch the dogs while they're gone, as it's expensive to board. I don't know if I should just suck it up and miss the midterms, and have my grade suffer, just because I'm sick of her acting this way. Am I the asshole? 