Just before 12 months Moo was really battling the arvo nap (and I really wanted him to keep it!) and I was feeling very frustrated, so big hugs darl.
In the end we just went with the flow. If he didn't have an arvo nap we put him to bed earlier that night. We found every few days he'd want an arvo nap for a couple of days while he transitioned. Now he just has 1 to 2 hours in the morning. Some days he still needs another sleep, I've actually just put him down as his morning nap was quite short today. Hoping he'll have a little kip otherwise it's going to be a very long afternoon!
It's hard when they change things around on you! Hope she sorts herself out soon.