One very sick vommitting cat - please help or give any ideas

[borov]

My adult cat (nearly 10 years old) is throwing up her food every time
she eat for the past few weeks. It's not hairballs..what can i do to
help her not throw up? She has become so thin, only weighs around 1.8
kg.

I have not changed her food,she has been eating the same food for
years.
I took her to the vet yesterday, he did some blood tests on her and
also took some x-ray, but found nothing wrong with her. He said he
could operate on her (open her up inside) and have a look, but I am
just afraid that she won't survive surgery. Plus who know if they will
find anything even if they open her up :~(

Please help me, I love my cat. She have been my best friend for the
last 10 years and I don't want to lose her, but I also don't want her
to suffer.

What should I do now? How can I make her better?

Any ideas, help is much appreciated.