As you can guess, I'm no expert
but I have always thought that 3 hour naps during the day are likely to rob from nighttime sleep - I always used to wake at 2.5 (but then had a 12.5 hour night, so comes to the same thing in the end). I would think, though, that the chatting and singing in the evening would suggest that she is waking up from her daytime nap too late to be tired enough for bed.
I'm still experimenting with getting the timings right - there's a lot of M's behaviour that has me thinking that she is OT, which I think is not surprising given how much sleep has been cut from her day recently, and she doesn't chat and sing when she goes to bed, but gets upset. I actually think that her sleep needs have gone down slightly, but that coincided with when we were away and she was unsettled, and from that she learned that she didn't have to go to sleep immediately when she went to bed. What I'm trying to do at the moment is get her used to going to sleep immediately again, and then I am going to try adding a little sleep here and there to try to get her to the right point.
For example, for the last few days I have been waking her at 6.30 to try to get her to go down for her lunchtime nap more easily at 12.30 - today I woke her at 6.45, and she has gone down very easily at 12.30 (having asked to go to bed!). I will probably continue to wake her at 2/2.15 for the time being, so I'm gradually trying to 1.5/1.75h lunchtime sleep and 11/11.5h night.