Yes, I've heard the potty thing quite a lot actually, definitely worth a try. I've also heard that it can help with night terrors too, which I did wonder if this was but it doesn't sound like it, especially with those timings.
I'm wondering if she might be OT or UT - any thoughts? Routine-wise, she's still having quite a long nap so it makes me think UT, but the wakings sound more OT to me. Is she settling ok at BT? If she's OT then it might be worth trying an early BT for a few days.