asleep by 6:15 based on what you are saying, even 6 since she had such an early morning (think 12 hour day no matter what)...
actually, this might help you, it has helped us.
instead of thinking of A time post nap at this age, think of 12 hour day, and A time in the morning. So wake, 5 or 5.5 hours of A time, nap, then in bed 12 hours from wake up time ...the only caveat is that if they have a nap less than 2 hours, then take that time off bed time. so for J who woke at 5:50 the day would be a bit like this...
5:50am wake
11:30 am nap (assuming 5.5 A time)
1 pm wake (assuming bad nap, only 1.5 hours for example)
5:30 bed (6 pm would have been 12 hours, but she was 30 mins shy of the 2 hour nap, so 5:30)
I know you are both rolling your eyes at the early bedtime, and it is extreme, but if you peruse the nap boards, the theory is that you would only have to do this for a little while to prevent OT while they learn to sleep longer in the day, which will improve night sleep and you get back to a more realistic wake and bed time.
hth a bit. we are just on the tail end of that and to be honest with you, we still have nights where they need to be in bed by 6:15 and it is hard, because that is just too early. but if we don't do it, we get even more out of whack...it's a balance of what you can do versus what you can accept in terms of bad naps/nights.
hang in there.