Well, they're talking optimum conditions when they say how big it will get...so you can't really expect to get that on your first try. It flowers for 9-11 weeks, and if its like most strains, it will do most of the stretching in the first three weeks of flower. If you had perfect growing conditions - soil, light, nutes, etc - you would probably be in trouble with letting it veg too long, but unless you have a real limitation in height in your grow room, you'll do okay. Most plants will anywhere from double to triple in height once they are done stretching, so even if she triples, you should end up just over three feet tall.
As for repotting, at this point it would likely be a big stress on her that you don't want to risk. You can remove some of the bad soil and replace with better quality, but you may do root damage if you dig around too much and that would set her back (or worse). I would advise letting it go as is, and maybe starting a clone of her that you can put in some better soil for the next grow.
-Mandi