Have you changed her food or diet in any way? Has she been put on medication for any reason? If not, maybe pull some blood work including a thyroid - it's a starting point.
I have 2 girls that are late coming into season. It's going on 9 mo. since their last heat but they aren't 6 mo. girls.
I don't have kennel facilities. Although the dogs are all indoors with us when it's been extremely hot, not out in the dog yard; I do believe the weather this year is affecting them. I have 2 others that came in early, actually 3 times in 13 mo. Those 2 usually come in every 5 months and 1 had a split heat years ago.
If things don't change in a few weeks I'm off to the vet.
