Should i harvest a sativa early? She looks ready

Barring extreme circumstances, you should harvest it at the ripeness you prefer. You put in 3-4 months. Don't lose patience now. Let the trichomes make the decision. plants don't really bulk up any more.. some have a trait to pop more pistils or some sort of stress possibly?, but then you also have vastly different ripeness of new growth vs old growth, so it's not all gravy. Each to their own on how to handle that.

To my eye it looks ready, doubt that without downgrading bud quality or foxtails you can get any mass into them. Now only maturity of trichomes will tell you...