i was trying not to consider this possibility o__o

I didnt even think sex was involved. Was it explained why she disappeared?

Because they both cant exist, gems cannot multiply, they cannot have a family.

There can be only one rose quartz gem, there canot be many pearls or jaspers or peridots.

When rose died for him, she gave him her gem, the gem must have memories of her because she lived through it and the gem was never restarted because he still have her weapons, but since hes organic, the gem cannot argue with his brain.

Couldnt she have kept the gem?

She couldnt, there can be only one of each gem.

Shes basically steven now.
Gems werent born to give birth, Rose was the first gem to ever give birth.