Renne, I think that Persephone's analysis of the situation that you decribe is spot-on.
This GG may have "clocked' you, but her reaction in scanning you so intently and in not showing any overt reaction either way - either negative or positive - was an act of tacit "approval", if not downright acceptance. She was clearly impressed by the way you were presenting yourself, your flair, your sense of style, and the great lengths that you had gone to in order to look as "passable" as you could as opposed to dressing like a drag queen and in a manner reflective of a cartoon-like version of femininity.
I'm also guessing that this GG was wearing the standard suburban soccer-mom uniform of jeans, runners, baggy, ski jacket-like outerwear, and with a large, satchel-like purse slung tightly around her shoulders, resting on her hips and within easy reach to put her into full "mall wars" power-shopping combat mode. And then she spots an elegantly-dressed "lady" who - Holy Sh*t! - probably isn't a "lady" at all but still manages to look absolutely stunning... so as the wheels in her brain are turning, the reaction vacillates between thinking "How dare he look this good?" and "Crap, I clearly need to up my game to play in the same league".
I once had a similar experience in a mall, where I suddenly heard hurried footsteps following me, only to have a GG pass me , wheel around, and out of the blue say to me "I hope you don't mind me saying this, but I just love your outfit!" Being caught totally off-guard, all I could manage was a "Why, thank you", while she followed up with a "Yes, you look absolutely stunning!" before hurrying on her way. I never did figure out if she had "read me" and thought I looked "stunning" as a crossdresser or took me to be a real GG, but either way, it was a mind-blowing comment that still makes me smile to this day when I think back on it.
So own it and savor the experience, Renne. You clearly knocked this GG's socks off, and I can say that with some authority, as odds are, she probably wasn't wearing pantyhose either.