I think there's probably no "right" answer to the OP's question. Some wg's might be very appreciative of your informing them, and others not so much.
In fact I remember reading about a similar situation, either here or on UKE, I don't remember which, where a punter informed one of his regs that he learned of her real name somehow, and she ended up dropping him as a reg because she was so freaked out that he knew her personal details.
Do what feels best to you, but realizing that you can't know how she'll respond....