Context is still key, here.

Who was it who'd stipulated that you'd get $7 and she'd only get $3? Was it you knowingly claiming 70% of the profit, from the onset? Was it an intermediary who broke down those percentages, in your favor, to intentionally give you an unearned advantage? Was the 70/30 split a onetime disparity; or was it intended to be how you and your female coworker would respectively be compensated (inequitably), in perpetuity?

In this case, the problem has been clearly identified. The solution is murkier. Yes, you handing over $2 to her -- in this moment -- is the fair and just thing to do, because the two of you contributed equally to the profit/revenue stream. Does that one-time gesture stave off a pattern of inequity, or is it merely a symbolic (or performative) gesture?

If this has been going on for an extended period of time, unbeknownst to you -- it doesn't make sense for you to give your female coworker reparations out of your own pocket. The right thing to do is for the backlog of money (to which she is entitled) to be garnished from the "broker" who oversaw the inequity.