She is too young.
Toy dogs take longer to mature. I wait till my Dams are atleast 20 - 24 months. They are mature, fully grown, and most problems will be apparent at this age.
And most important is their health. The first season is around 7 mos, their still puppies. Let her mature, it'll be better for her health and the health of her future puppies.
Good Luck
