assertive female
A milder version of femdom. A female character who is sexually assertive, in control of her partner, or romantically active.
For sexual interactions, this is typically when the girl is on top or clearly in control - no frowning, gaping, blank stares, etc. - often with a naughty expression. Basically, she is screwing her partner instead of the other way around. If the partner is also shown to be enjoying it, it might fit better in happy sex.
For romantic interactions, the girl is actively displaying affections towards the partner. This does not require any agressive, sexual, femdom expressions, as long as she's the one that's initiating the interactions. If both partners take turns in activeness, this is also a reversible couple.