Wow - that sounds very similar to my daughter. We were there until about a month ago and it was NO FUN! We tried everything in the book to get her to poop and incentives did nothing. She was holding, too.
You could try giving your daughter a liquid suppository if she is holding just to clean her out and show her that she can go on the potty. My threshhold for this is every 3 days, but you know your daughter's system best. I think the more they go on the potty, the less scary it is or the less control they feel by holding. The box says it takes 15-60 min, but I found it to be much closer to 15 minutes.
I would keep her on the miralax until you are over the hump because hard poops can hurt and that will only make her want to hold more. You could also just cut all of the cutesy games and incentives and tell her she has to stay in the bathroom (not necessarily on the potty, but in the bathroom) until poop comes on the potty. It sounds mean, but it worked for us in a surprisingly short period of time.
Good luck to you!! Potty training is no fun, especially when there are delays and resistance!