In MY opinion, and it may be deemed "old hat " by some people.
I would always allow a female dog one heat before having her spayed about 3 months afterwards.
Although this is not always convenient especially if intact male dogs are kept in the same house or live nearby.
I don`t believe that spaying or castrating dogs before they are fully mature is the best thing to do, as they need all their hormones for maximum healthy growth.
However, if there is any possiblity that your female dog may come into contact with any intact male dogs I would recommend having her spayed NOW before she has a first heat.
There are many benefits to having a female dog spayed, including much less risk of mammary cancers. No risk of Pyometra and no messy bleeding when in heat.
Cons are few ,but it can be that some females can be a bit more lethargic and put on more weight than an intact female and often (not always) grow a coarser textured coat.
All non-breeding female dogs kept just as pets should be spayed.
54 years of owning GSD`s.(male and female)