Hi there, yes she certainly could be coming in to season, German Shepherds come into their first seasons anywhere between 6-12 months, I have a young GSD in season at the moment, she is 10 months old and it is her first, she was very quiet beforehand and I noticed her vomiting a couple of times just before I first noticed her bleeding, she is in her 2nd week now and has been sick intermittently right through but this would probably be 'normal' for her, except I am getting her spayed ASAP. Remember all dogs are different. I have kept GSD's for 30 odd years and none of them have been the same!
Just keep a close eye on your dog and of course if you are worried, give your vet a ring, they will advise you.