Is Roxy spayed yet? Is there a possibility she could be pregnant?
Hard to say what it could be, if
it is an infection know that they can spread rapidly and the sooner this is looked at and treated the better the outcome. Since she is chewing at the area it does sound like it's bothering her to some degree, any chance you could have her in sooner & work out a payment plan with the Vet's office manager?
& let us know how she's doing