I don't know what to do

I apologize in advance if this post isn't appropriate for this group; I just don't know where else to turn.

I (30F) recently found out that my mom (62) might have cancer in her brain, which would have spread from what they originally thought was a dermatofibroma above her eye. They don't know for sure if it's cancerous, but it seems to have gotten worse pretty quickly and she's supposed to have surgery to remove as much of it as possible and find out if it is cancer on January 29. I'm really worried because it does sound like she has a lot of symptoms that match up with something that's spread to the brain.

I was supposed to move abroad / overseas to close the distance with my partner of 5 years in March; I literally just got my visa approved and now I don't know what to do. I'm an only child and we don't have any other family in the area, so it's just my dad (65) who would be caring for my mom if something were to happen.

Right now, I feel like the only thing to do would be to stay here and care for my parents. I don't want my dad to have to deal with this alone and if something happened, he doesn't have anyone else here. I guess I just feel a bit shocked by everything and I feel selfish for being upset about giving up the opportunity to move abroad. My partner and I have been waiting for this for a long time and I've been planning to study there, working on the language etc. If I don't go this time, I think our relationship will eventually come to an end as well, as there's not really any other way for use to live together. I also don't think I will be emotionally able to be in a relationship at that point, either.

I know it's an individual decision, but I just wanted to get a sense of what others in a similar situation might think is the right thing to do.
Thank you