Glad to hear all went well at the vets today. I took my Jack in today for his routine stuff - vaccine boosters - he's set for another 3 years now! All went well.
I would seriously consider spaying her - as the others have said, you don't know if she is pregnant, what kind of dog mated with her and that could be a real problem. You mentioned you thought ultrasound sounded expensive - in my opinion, that would be pocket change if this little one is pregnant and has a hard time delivering - you are looking at emergency C-section and then all the expenses that go along with having pups (tails docked, dew claws removed and vaccines). I would recommend that you review the breeders section here for more information.
As far as having her sprayed "before the hormones come in" she is old enough at this point - she will just retain some of her puppy like qualities (which is not a bad thing). I had my Jack neutered at five months and Izzy spayed at seven months. So far, they are wonderful and I don't even miss the hormones that could have come in
Good luck - oh and did we go with Rogue as her name?