C.B.
change gears immediately. somehow she has gotten the idea that moving is huge and scary. she didn't come up with that herself. perhaps in trying to "prepare" her you've opened her up to the idea that there's something to freak out about. my son regressed when we moved, but not until it happened. we made it very positive and called it an adventure. we got a yard for the first time so we played up how he would be able to play outside...he did okay and seemed happy and excited, but after the move started "spotting" his underwear, and stopped being dry at night. i bought pullups again for night time (urgh) and eventually, when the "spotting" didn't stop after several weeks, went back to square 1 on potty training, with the sticker chart and all. it only took a couple of days before he was "too big" for the sticker chart, and he nailed it. i say stop talking about the house all together if you can, return to the "status quo" for her, and WHEN you have to bring it up, make it fun and exciting, talk up her new room, really make it a fun experience. in my experience (although every child is different i know that), as long as they know that mommy and daddy and they wil always be together, they'll be okay. does she realize you're not leaving her AT the old house? it doesn't sound like it! i would let it go for a few days and then readress it with a good heart to heart. once she realizes she's going WITH you then maybe she'll feel better about it. and whatever you do, DON'T make a big deal about the accidents. she's anxious enough.
ps, one thing that has always helped my son gear up for changes is telling it to him in a bedtime story format - he LOVES me to tell him a bedtime story, so i try to make it constructive if i can. i tell him about the "little boy who got so big that he woke up in the morning and put his clothes on ALL BY HIMSELF!" (yeah he thought that was kinda lame), or, about the little boy who went with his mommy and daddy for a long long drive and they ended up at a beach...so maybe an adventure story about the little girl who helped her mommy and daddy put (all her favorite toys) in boxes, and then put them in a truck, and THEN took them to a new house, and opened up all the boxes....etc etc etc....and how big she was and how brave and how much FUN it was...might help!