If you start getting her up all night to try to pee, you will be training yourself, not her. It would be very likely to also start a power struggle between a very tired little girl and a very tired mom. I believe you would lose ground, not gain.
I think it's great that you have gotten her using the potty for the past 6 months during the day, and frankly, I think we focus just a little too hard on trying to get kids potty trained. I do not know of a SINGLE 15 year old who is still in diapers, no matter how potty training went or how early or late it was done! Tee hee.
Sophie will gradually gain enough unconscious control of her bladder, and her bladder will get big enough with enough sphincter control to get her through the night. She sounds like a physically large girl since birth, so maybe that's more of the issue--but there are diaper like training pants for big kids that are large enough for her and there isn't really much difference between them and diapers other than your personal feelings about them.
One thing you might try in order to move things along a little bit would be, for example, if you put her to bed at, say 8pm, then, right before you go to bed, have a quick "Mommy/daughter time" that includes going potty. Get up at maybe 6am, for another try. This will, over the space of a few weeks, maybe less, get her system trained so that it "knows" the times she will be able to go, and you can go from there. It's likely she'll be dry pretty soon, either way.
Fiora