A.H.
Some times taking a step back to when she first started would be a good start. I potty trained my son when he was about 2 and a half. I took a week off of work, we got him some big boy underwear, ( I personally don't believe in Pull Ups. They are good for night time until they are old enough to not wet the bed but to most kids it's not much different than a diaper) I kept him in the kitchen, so clean up would be easier than it would on the carpet and dressed him in just a shirt and underwear. I took him to the bathroom every hour on the hour. If he doesn't go pee for a couple of hours I would keep him in there until he does by singing the ABC's or looking through books. If he started to pee in his underwear I immediately took him to the bathroom. After about 3 days he was potty trained. On the fourth day we were asked to eat with family, and I was unsure but we went anyways, still in underwear but I did put him in pants. As we were standing in line, he said he had to go potty and he held it until we got to the bathroom. When he came out he was so proud of him self that he announced it all the way back to the line that he peed in the potty.
I also do not agree that it takes boys longer. I think it has more to do with the individual child and a lot with the parent.
With my daughter I intended to do the same thing. However, I didn't plan well enough to be home all day for a few days, on only the second day we had to go to the store so I put her back in the diaper just in case. It was because of my own inconsistencies with her that caused her to take longer.
If she is having problems, he has developed a new habit of not going until it's too late. And if she is getting frustrated at all at the situation that is why he is not telling her. She just needs to take a step back and re-instill the habit of going right away by taking him to the bathroom every hour or so and making sure not to wait until it is too late and making sure that if they go out of the house she takes him before they leave and makes sure to take him to the bathroom while they are gone.