Michelle didn't even start the process until 2 1/2, and was not dry during her awake times until after 3 years old. Now, at almost 4, she still wears a diaper at night, and still wakes up wet 1/4 of the time. We really pushed hard with #2, because she had constipation so bad she was having rectal prolapse issues, because her stools were so hard and big that the diaper would hold them in.
Her sister, Nicole, is 2 1/4, and has been ready for some months now, much earlier than her sister, but dang it, I'm about to give birth, and there's just no way I'm going to be in the midst of potty training with a newborn.
It sounds like Gabrielle's just not really ready yet. Both of my kids like to have their favorite stuffed animal go pee and poo in the potty, and then use up an entire roll of toilet paper wiping their stuffed animal's butts. I've also informed them that the first thing Dora (insert child's favorite character here) does in the morning is they go pee on the potty, just like mommy and daddy. In fact, did you know that all of her favorite book characters pee on the potty? They do. I swear. They don't wear diapers, either. Because they're big girls. (sigh) If only such logic worked on thumbsucking...
Talk to the preschool. Usually, they're pretty accomodating.