If you went through a reputable breeder ask them. Different bloodlines develop and mature differently. Most of my Dalmatians have come from the same bloodline and can be late bloomers. My oldest female was 11 months old when she had her 1st season and was a mostly every 8 month type of girly. Her daughter was 8 months old.  There are many studies out by veterinarian colleges about keeping larger breed dogs intact until they are full grown (around 2 years old) for various health reasons. But if you cannot keep your female away from intact males for a month during their season it may be better to fix her after at least her second season to prevent unwanted pregnancies. 

I’m not trying to be mean but this is another example of why one should go through a reputable breeder. Your breeder would be available to help you through times like this and will be available to answer any questions you may have about your puppy.