Is this really my fault?

My best friend and I got into a big fight last night and she claims it's all my fault. See, her birthday is on Monday and I told her we could do something together just the two of us like she wanted.

Well, last night we were talking and I told her about everything that I wrote in my last journal. You can view it here but if you don't want to read all of that (Which I don't blame you), long story short I have like a stomach virus or a bug or something like that and I didn't go to a camp I help out at every weekday for the summer on Friday and I left early Thursday because I got sick there. She knew that too. Then later in the conversation I said that I would be back Monday because It should be gone by then since it's going away right now. When she heard that she freaked on. She started yelling at me because she made a lot of plans for Monday (the day of her birthday) for us to hang out. But it's a weekday and that means I go into the camp. She's mad at me because I won't take the day off since I took off yesterday and It's my last week there next week for the summer so the least I could is stay for the whole week. Even though she knows that I have been doing this and I'm busy on my weekdays she still had to plan it for Monday instead of sometime during the weekend.

I told her that we can do something next weekend because I don't feel well right now and I'm doing something during the weekdays but that's still not good enough. But I'm the selfish one here. It just HAS to be on the day of her birthday even though last year and the year before that she was fine with celebrating it a week later but not anymore the year that it's the best for.

So now I "don't care" about her or her birthday and I'm a bad friend.

Seriously, is this really my fault?