If you're concerned, you should take her to a vet who knows birds or livestock. They'll be able to figure out what's up better than a common small animal vet, as they focus on cats and dogs. I'm not sure what her problem could be, but I wish you luck.
I can't help but comment: A cat or dog is worth how much? And how much does a vet charge? And yet, people take them to veterinarians. Or at least they should if they intend to own them. A chicken is a form of life and therefore deserves medical care if it isn't feeling its best.
Lord! I'd hate to be a chicken vet!
When a chicken is sick, they often don't live through it, I have had many sick chickens (around 30ish in my life) and only one ever survived. Although when I have taken them to a vet, they have lived for longer then they would have, or the vet puts them down it they can't survive.
I'm not sure on what your chicken has or anything, but its better safe then sorry eh? It sounds like he/she just has the runs, but that can be fatal as they have terrible immune systems. The strength of the immune system can also depend on the breed of chicken.
Completely agrees with Shelbie, they are a form of life just like any other pets.. unless you own a rock.. they don't need vetting : /
If he or she is sick
Your chicken is worth how much? The vet will charge how much? Do the math.