AITA for not wanting to cancel/rearrange our summer trip because one friend cant make it?

Okay some establishing facts. This is about me and my two friends, A and B. Both my best friends. A lives in Germany like I do, B lives in the UK. We lived there together for a while.

Since I have been back in Germany I chose a more artistic livestyle, which affords me more time for art, but less money since I don't work as many hours. And the hours I do work are all over the place, because its in service. However its worth it, because I struggle making friends and I have some lovely colleagues my age and finally feel like I am somewhat arriving. I still dont have any close friends despite A and B though.

Now, since its so hard to get all of us to each others birthday parties and I knew B was sad, that I couldnt come to the UK for financial reasons, I came up with an alternative some months ago. B is very integrated into my german family, she especially loves my dad and has expressed that shed love to see them this year. So I suggested, why not do a little celebration at my parents and since my dad owns way too many tents...a little summer camping trip by a lake.

To be honest, I had been wishing to have close enough friends to invite to something like this for a while and after some scheduling and planning, I managed to get the time off, my dad booked a camping place and I was really excited. And I could tell he was happy I asked him along, we live on different ends of the country and dont get so much time together.

Now B has developed a health issue with her foot which is very scary for her and as long as its undiagnosed, she cant fly because she wont be able to get insurance. I understand it really sucks...and I was sad that I might not get to see her. Now A approached me and said she was feeling guilty about doing the trip without B (which I get) and asked if maybe we couldnt do something else, fly to London maybe. But my financial situation hasnt changed. I can manage really well but thats because I am mindful about my money. And tbh Id feel awful towards my dad. Plus, I do wanna see him.

B then also texted me, saying we needed to talk about the trip, saying that she felt left out for something that is out of her control. She said it was meant to celebate our birthdays together and that she would like to talk about what to do if she cant come.

I replied that I didnt really want to cancel on my dad and that maybe Ill go with just him. Because A had already hinted towards maybe making plans with each of us individually but not coming along to the trip because she felt guilty. I think B is mad at me now...but I am also sad, I was really looking forward to finally have a friend along. Something about this makes me feel lonely, but then again, maybe I am the asshole here, I dont know.