Do you have a gro clock? I found using that at nap time used to help when lily was that age. I used to set it for 45 minutes from her nap time, pop her in her cot with the lights dimmed, some soft toys and books and say she had to stay there playing quietly until the sun camepup and that she could sleep if she wanted to. Sometimes she fell asleep that way, once the expectation for her to nap was gone. Other times she wouldn't, but at least it was restful, quiet time (for us both!). If she fell asleep I used to creep in her room and set the sun to come up at a later time. You could do the same with a timer if you don't have a gro clock?