cats with colds going to vet ?

Those of you who have had indoor cats for a while I need advice.

Miss Kitty is 4. Had her annual exam and checkup about 6 weeks ago.

She has been sneezing for the last 2 or 3 days. No eye discharge but today I notice her eyes are somewhat watery. She came from a pound and had cat flu and conjunctivitis as a small kitten.
She is eating, drinking, pooping normally and seems almost as playful as normal.

I certainly wont hesitate to take her to the vet is this continues. However, how do you decide when to take your cat to the vet. I hate to pay $75 for a visit if she only has a cold that doesnt need meds.
charlotte