Feral Cat Vomiting and Wants Water. Help?

Hi, it's me again. Hoping for some quick advice, as it's too late for a
vet tonight. One of my recently adopted feral cats has been doing a lot
of vomiting today and I'm getting concerned. She's not vomiting food,
just small amounts of white stuff, like spit. When it started, I picked
up the food and water dishes, to get her system to calm down. It doesn't
seem to have helped much, she's still vomiting about once every 90
minutes or so. The thing is, she's desperate for water, and keeps
running through the house looking for it. Should I give her a little so
she'll maybe settle down, or continue to withhold it? Any other advice
would also be helpful, because she's still pretty feral, and putting her
in a carrier for the vet will be extremely traumatic for her, if it can
even be managed. She permits gentle petting, but nothing else, we can't
pick her up or handle her yet. Help?

Thanks,
Robyn

--
To avoid grizzlies, the Alaska Department of Fish & Game advises hikers
to wear noisy little bells on clothes and carry pepper spray. Also watch
for signs of activity: Black bear scat is smaller and contains berries;
grizzly scat has little bells in it and smells like pepper.