2 naps to 1

[Deduct37]

My 16 month old is having bizarre days with her naps. We've had a few days where she has woke around 6ish, had a nap at 9 ish for 1.5-2 hours then refused an afternoon nap so has stayed up until bedtime (which I've brought to 6pm).
Then we have had days where she hasn't had a nap at 9 but fell asleep around 10 but just had 35 mins.
We've also had a day where she fell asleep at 10.45 and had almost 2 hours, but then days where she's fell asleep at this time and only had a catnap making it too late to try for a second nap.
She has never had a fully structured routine due to her wake up time varying from 5-7ish and also due to the length of naps.
She has had a few grumpy days which I've sure is due to her being overtired. She wakes up crying most morning, although we have had a few mornings where we watch her in the monitor playing with her teddies. She can then be clingy and wingey most of the morning until she falls asleep.
We've tried keeping her asleep in the mornings but this doesn't always work. Lately wake up time seems to be around 5.45-6.15. (Which is usually 12 hours with going to bed soooo early). We've tried keeping her up until lunchtime etc but some days she would only catnap and wake up in a foul mood. We've tried later bedtimes but it seems to backfire. We've tried capping the morning nap but then her second nap doesn't seem to be any better. I feel we've tried everything. Can anybody see what could be going wrong? I know I can't complain because she's getting good night sleep, but she still seems tired after this and I can only think it's due to her naps

[luckiestgirlintheworld]

My 15 month old has a bedtime of 6pm too (I love it!) and only has one nap. He gets tired about 4 hours after he wakes (which at the moment is about 11am because he's in a strange phase of waking at 7am so getting 13 hours at night. But it used to be he would wake at 6am and nap at 10am.)
His nap is about 1 to 2 hours long. Then he seems to be fine not having an afternoon nap so we just cut that out.
Perhaps if you moved to one nap then she would sleep longer at night and wake later a bit more consistently, which might mean she's a bit happier in the mornings?

[inaboxwithafox]

Maybe add some structure....no naps in the morning, early lunch and put down for nap at 12pm? After a few days she might realise that this is rest and recharge time. I know you said you've tried but maybe worth persevering? If she's only sleeping once during the day it makes sense to split the day in half.

Ds is 16 months old. Wakes at same time as your daughter (up by 6ish), nap at 12.15 and he sleeps for about an hour, sometimes an hour and a half, then push on to bed time at 7.30pm.