C.C.
i had to smirk when reading this b/c my daughter was THE SAME exact way. we did the miralax and glycerin suppositories, warm baths, exercising, fiber therapy......everything! but, the good news is she can't hold it in forever! keep giving her the miralax, feed her high fiber foods, try a little prune juice and wait it out. give the suppository a break for awhile. maybe she's upset about that or something. you just never know with kids!!
anyhow, as hard as it is, be patient and try not to think about it for a couple days.
trust me, it might seem like forever away, but she'll be using the potty like a pro before you know it!!
also, have you tried bribes? we told my daughter that when she started pooping in the potty we'd take her to the store to pick out something special for using the potty like a big girl. she chose a care bear and still sleeps with it each night. also, m&m's work great, too, if she likes chocolate. i would give mine about 4 for pooping. it was motivation enough for her.... :)