Blimey, *hugs* to you, I know how it can be as my LO used to do this 10-midnight!! We figured it was because he was not tired enough to be sleeping. But I think as your
little one (LO) is 12months old, 6.5hours is a bit long to go before bedtime! My LO is 16months now and can do 6hours at an absolute push. Have you tried moving the morning nap later in the day?? If she's getting up at 8 and going to bed at 7pm I'd expect maybe something like this:
A: (Awake) 8-12:30 (awake for 4.5hours)
S: (Sleep) 12:30-1:30
A: 1:30-7 (awake for 5.5hours)
Or even put the nap right back at 1-2...?
I think it could very well be over tiredness at bedtime. My LO wakes a few times before midnight now if he's too tired at bedtime. Is there any reason the nap is so early in the day? If you need to keep it that time could you move bedtime earlier, which will mean wake-up earlier and the nap stays the same time?
Hope that helps! (HTH) There are some people on here with a lot more experience than me on here and I'm sure thy'll be along soon to help a bit more
xx