White females boxer, about 10 months old- still no heat?

I recently got a white female boxer from a relative of my boyfriend. She was malnourished and had been treated badly, and i am trying to get her healthy. She still has not had her first heat, and is about 10 months old. The vet told her previous owners that she may not have one until about a year old. I was just wondering, since most of these dogs start at about 8 months, if her health could be a cause as to why, or is she is just a late bloomer? We would like to breed her, and will be visiting the vet prior to any of that, but I am a little wary of doing it at all if there is a chance it could endanger her health. Does anyone have any advice or suggestions?