Well, depending on the persona you convey, in addition to the answers provided above, deliberate anachronism can be used, if used with finesse and an appropriate audience.
If you're funny, for instance, you may be able to sell "I met this dame, Watson, and I haven't been the same ever since," Or "dude, I was talking to this dudette..." It would of course be in the presentation, and whether you have a reputation for humor.
Even that aside, the way you roll the phrase is going to affect the interpretation. Saying "I met a lady" is awkward, but saying "a lady at the cafe..." rolls better. Saying "I met a woman" is also awkward, but "this woman I met..." is less so. Often, it simply boils down to what we're more used to hearing, and the ineffable cadence of poetry, and that too can affect the perception of propriety. The greats of poetry would likely be able to call someone simply "female" but in a way that would seem smacking only of admiration.
But... If you're looking for one single answer to be politically correct in a business setting regardless of presentation, and that specifically conveys gender, then you're going to have to use "woman" however awkward you may find it, or, you're going to have to re-examine your approach.
Think about what's really important here--what is the person to you? Is she really a woman, first and foremost? Based on the situation you described, probably not. From what I gather, to you she is currently a "business contact" or potentially so. You should lead with that, and then clarify her gender if you really feel it that important. Communicating information in order of importance is generally good practice in a business setting.
"I met a potential business contact today. She was around my age, and had keen thoughts on the widgets we sell."
Honestly I think this would be the best approach.