My cat's whisker area is swollen. Should I wait or see the vet?

This type of swelling could be something fairly simple and harmless such as an ingrown hair or an insect bite, or something more serious such as a localized infection or even a skin tumor of some kind. If the swelling doesn't seem to be bothering her and she is acting normal otherwise, you could wait to see if it goes away on its own within the next week or two. If it doesn't, or if it gets larger or becomes itchy or painful, then I would recommend having her examined by a vet to determine what it is - he/she may prescribe antibiotics or short-term oral steroids to treat the swelling, or may do a simple test called a fine needle aspirate to diagnose the problem if it appears to be a growth of some kind.