Maybe this is her way of saying she is not ready. My girls were almost 3 and it took 4 days and it was a cinch. Stayed home all day and just peed when they had to go. I let them be in control of their bodies and what it was telling them. We have never had an accident out or in the car or on errands.
Also it is not good for her to hold it in for so long that can cause bladder problems like UTI's and even worse.
We used undies or naked all day and then diapers at nap and bed, they wet those a lot in the beginning but the rest of the day they were using the potty. The diaper or pull up for nap and bed are a lot better than a wet bed. Then as they get older and the nap diapers are not wet switch to undies then as the night ones are dry switch to undies. I still at almost 5 years old take my one to pee every night before I go to sleep, 11pm, or she will have a huge accident in the middle of the night. The doctor said it is like 5 before they have that much bladder control to hold it all night. I know it is stressful but relax they all train or we would have a world in diapers, coudl you imagine,LOL.
I tried to potty train at 15 months and things were going smooth but then it was traumatic for one of my girls so we just stopped and went back to diapers even though one was almost trained. It was too much work and too stressful for them and me.
Good luck!