
Without seeing her it is impossible to tell, but I had a similar experience with one of my dogs. I found he would rub his chin on the floor and on his legs when he "doggie acne", he would also do this when stung by nettles if he had been hunting round in rough grass. I assume both things made his chin itch.
Really though it is best to get anything that worries you, checked out by a vet, if you didn't and it was something serious developing you would never forgive yourself, so best thing is look silly and embarassed rather than mess about too long.
regards Polly & the Foxpath Flatcoats.