Sorry gals, but the gender-verifying bouncer must've been looking the other way.
If I may toss in a guy's perspective - once we know we want to kiss a girl, we REALLY want to kiss her.
I think a potentially good way to deal w/ this problem is to not mention it at all until a kiss is imminent.
Strange as it seems, even waiting as late as the lean-in may work best. (As long as a sink or whatever for brushing isn't too far)
At that point, the engine's revved up enough we'd often be willing to do a lot more than just brush our teeth to get 1st lip-to-lip contact!!
Of course, celiac would've already come up. So, in backing away from the lean-in, something like "remember that stupid disease? I can't kiss you w/out being certain it won't make me sick".
Whip out a cheapie toothbrush from your purse, (in a baggie in there maybe? I've seen 4/$1 at a dollar store) and I guaranTEE he'll brush harder and more thoroughly than ever!!!!
I seriously cannot imagine this ever failing. And I have quite an imagination!!
Even if you're outdoors w/ no sink around, all you really need is a bottle of water, right?
The guy is WAY too revved up in anticipation to not comply w/ something as simple as a brushing!!
I predict no shortage of smooching in Lisa's future.

[Edit:
P.S. WTH!

I didn't even realize I have the same problem!! After being mostly house-bound for years I'm back out there, but all I'd wondered about was how I can possibly handle asking some fantabulous woman whether her lipstick is gluten-free!!!
Now I've got to worry about teeth too??
This thread's topic is truly not at all limited to just females or teens.
This old guy has same problem.
Grrrrr that a woman I met yesterday has a boyfriend. She wasn't wearing lipstick or even any makeup at all as far as I could tell.
<must kill bf> ]