Ajanta wrote:

I have a cat that visits me and I feed her more or less
regularly. Of course she is not my pet, so I don't control
everything she eats.

Is she spayed?

Today, whlile she was just sitting around and before I could
give her food, she started vomiting. ... I was confused and
decided I should not feed her today... we did the right thing?

If she isn't spayed, maybe you did the right thing.

So, for my future reference, should a vomiting cat skip a meal,
as I would myself, or is it different for cats?

I do not really agree with your premise about humans needing to
skip a meal.

I don't think cats should skip a meal. Cats vomit fur balls. They
might vomit also because of intestinal/digestive problems. In the
latter case, maybe their diet should be changed or maybe they
should be taken to a veterinarian. When concerned, I carefully
examine my cats vomit for hairballs to see whether there is a good
reason or whether she might need help.

Good luck.