Cat licking Spay Incision

hey i have a cat that just got spayed, i have read on many site that the cat shouldnt lick the spay site but i also hear it is her just keeping it clean. It has become red and swollen. is this normal or do i need to contact the vet.

Cats shouldn't lick their incision.  You will need to either put what we here call the cone of shame on her which cats hate.  You can also get a baby onesie and put on her to cover the incision so she can't get at it.  Some kitties leave the incision alone and others are like yours and need something to keep them from licking the incision.