I generally try to keep the same nap time, it helps to regulate them and if you keep the same time it might actually help her nights. I think you are in kind of a UT/OT situation, so UT for the nap so it's not overly long/restorative, and then OT by the end of the day because nap wasn't long enough. If she has a bad night and absolutely can't make it to 12:30, I'd just try for a 15min CN in the morning...in the car or something.