Fleas and scabs on my dogs back?

We had our 1 year old bordie collie staying with friends with another border collie while we were away on holidays. 2 weeks later we came home and she was covered in fleas (currently being treated for). Most of the fleas are now gone, with the exception of a few. What I'm really worried about is an increasing amount of scabs on her back. When we got her back she had about 5 small scabs that I umed was from rough play. Over the last week they have progressed about 1/3 of the way down her back and starting to go down her sides a little. I was thinking it was mange but she hardly has any hair loss (Except in the direct vicinity of the scab) and it is only on her back - read reports saying it is usually on legs, belly, chest but not back. She's not really scratching too much anymore either as the fleas are going, and she doesn't seem phased by these scabs. They're red, some just a bit smaller than a 5c piece, and a lot of flakey skin. She is booked in to see the vet tomorrow, but just wondering if anyone knows what this is? She is still herself, not off her food, and still as energetic as always. Thanks!