My son potty trained at 22 months. We set a timer for 15 minutes, when it went off it was potty time. I showed him where to push/squeeze by placing my hand on his tummy. We only sat for a minute and he got a m&m even if it was just a drop. After a few weeks we set the timer to 30 minutes, then after that he was going on his own or telling someone. Stay consistant. Sitting there is boring in the attempts to catch something. What you should try is establishing breaks so she learns what it feels like to go.
If its any help my son trained on poop within the first 2 weeks since he went right after breakfast and we knew the schedule. We also kept him naked from the waist down to ease the transition. Underwear, pullups, or diapers are worthless when potty training in my opinion. As long as they can feel something that will catch, it makes it extremely difficult. During the summer we just did shorts and then this last fall we added underwear in again. It was to much to get down in time to go. Toddlers are clueless to holding bladders and I was getting frusterated with the accidents in front of the toilet everyday. He just turned 3 and has been wearing it all, doing it all for 8 months. Good Luck!