My cat will not eat, it's been four days?

Call animal control - their officers are trained in a device called the loop - it's a long pole, with a loop on the end. They snare the cat (or dog) tighten the loop, and then put them in a crate - with gloves. Sounds cruel, but it's probably the only way you're going to catch her. Warn the vet before you take her in, as they'll probably need to gas her down prior to examining her. Good luck!