Congrats.... and Welcome to BYC!
Is she 16 weeks or closer to 20 weeks?
Not sure about silkies, but not unusual for other breeds to start laying that early.
Was there a yolk in there?
All pullets lay small eggs at first, can take days, weeks, or months for them to get as large as their 'normal'.
Fairy, fart, wind, rooster eggs are usually from a tiny piece of tissue breaking loose from the reproductive tract, or an immature ova(yolk) and the body forms an egg around it. Color can be darker than 'normal' as the pigment coating released has to cover a much smaller area so is thicker. Can happen with any age layer, but more common with new or older layers.
I think it's explained in this excellent video, which is worth watching regardless: