There's not really a magic number. Sure, studies show that things tend to happen at certain ages and as a community, we recommend certain ages and such because it is typically healthier for the animals involved. But there can always be exceptions. One of the saddest storys I know is a human girl who gave birth at 5.
There have been female BPs that breed when they are younger or smaller. I saw one girl at a pet store who laid eggs when she weighed around 1000 grams. But of course I don't know her age, only her size.
There definitely is the possibility that your girl is ovulating. Most likely she'll reabsorb instead of dropping slugs. Obviously, we will all still recommend waiting until she's at least 1500gr. and at least a year older.