Is there any way you can ask her breeder when her mother came in heat for the first time? I have noticed with dogs (and humans) that they tend to follow what their mothers did. I used to think it was size dependant until I had a toy poodle come in at 10 months and a Kelpie (adult weight of 32 pounds) come in at the delicate age of 6 months!
Any female I get now, I ask the breeder when her mother matured. That way, I have an idea as to when to start watching for it. Hmm, that reminds me - time to start keeping an eye out on Treasure.