Its so hard. You just cant force them to sleep.
Sounds just like Keira at that age. I would put her to bed just after lunch it would take a few hours to fall asleep and by then shes so tired she'll sleep right through untill dinner time. I felt she was missing out spending so long in her bed, but she really needed the sleep.
We tried so many different things, really tiring her out in the mornings, putting her to sleep later. Eventually the one thing that did work was one afternoon DH had friends around one of them walked passed the bedroom, poked thier head in and said goodnight. I think it scared her a little so she slept. Mummy and Daddy are too easy.
I think we had a few days of other people putting her to bed and then she was so used to sleeping straight away she just did it.
She did eventually start taking longer to sleep again and by this stage she seemed to be able to cope better. It became quiet time for a few hours rather than nap time, just so we both got that break. It also meant once we dropped the day sleep she went to bed earlier so was able to cope without that nap.
Sleeping problems are tricky, I hope you get it sorted soon!