Yes, 10 - 14 days is the norm. But, because this is her first cycle, it could be different. Maybe shorter, maybe longer. I usually keep my girls away from any willing males (and they're ALL willing when they're within 5 miles of a female in heat) for at least a month and a half, especially when the girl is still a pup. It takes them awhile to learn how to snap and snarl and make the boys understand that no means no!
Good luck -- it ain't fun. And no, this doesn't happen once a month, it usually occurs every six months. Usually. Can be more time or less. And my vet will not spay during a heat cycle, we have to wait six weeks after the heat ends.....