Let her run pantless. Keep a potty nearby. If you see her starting to pee, swoop her up and get her on the potty. She will probably stop going from surprise. That's OK. And she probably won't finish on the potty. That's OK too. She'll catch on soon enough... get that funny feeling, pee is going to come out, let's go to the potty so the pee can come out in the potty!
And remember, telling you she has to go or answering "yes" when you ask is one of the LAST steps in potty training. Don't ask her and don't expect her to tell you for months and months. TELL her "It's time to sit on the potty".
at 2:18 PM on Feb. 20, 2009