I Feel Very Conflicted

A friend of mine who recently got a cat kept telling me how cute and goofy it is. While she was rambling about the cat's cute antics, she mentioned some things that I, who has owned cats all my life, found worrying. Mainly the constant pacing and pressing head against stuff.
I told her to get the cat checked, and it turns out the cat has prosencephalon disease. Thing is, now my friend is really upset with both the situation and with me, for some reason. She had really fallen in love with the cat, and now I feel almost guilty taking that joy away from her.

I know it's only right to get the cat help, but I don't even know how you treat that disease. What if the cat has to be put down? What if the vet's bill is really high?

I know I shouldn't regret it at ALL, but I sorta do... 😩