Laney, this is about the right age for the 2-1 nap transition
I think if 45mins in the morning is no longer getting a longer pm nap then you could try 30mins in the morning & then another nap 3hrs later with bedtime about 4hrs later.
Its also ok for long morning nap & shorter afternoon catnap... so if she sleeps 1.5hrs in the morning, her afternoon nap will only be about 45mins cause at this age about 2hrs during the day & 11ish hrs at night is just about the av.
You can go cold turkey and go for 1 nap around 11-11.30am but I have to tell you that 1.5hrs is pretty good & its not always you get a 2-3hr nap. If she's sleeping 11-12hrs at night then 1.5-2hrs is just about right. Our nap only started with 45mins tbh so 1.5 is much better than that. If you are tired of 2nd guessing how much she will sleep & how long naps are, etc.. & if she seems ok to be on 1 nap then start with 11.30am & stick to that for about a week to see how she handles it. I just want to say that pushing the nap to 1pm is not such a good idea as the stretch is too long & if you do that over and over again she will probably get overtired. The av A times for toddlers when on 1 nap is about 5-5.5hrs. At the start we could only push to 4.5-5hrs A time before the start of nap & about 5hrs before bedtime.
So to answer your q's
Could it be that 12 hours of night sleep would make the one nap just 1.5 hours?
If she's doing 12hrs at night, you probably wont get a nap longer than 1.5hrs (unless she's had more than av sleep)
Or is it just that she needs time to adjust to this whole thing?
Give her time to adjust & if you want a longer nap then either consider waking her up earlier or push bedtime about 15mins late (every 4days or so) & NOT let her "sleep in" so that the hours then add onto naptime sleep.
Or maybe should I keep with 2 naps a while longer, and maybe try to go back to 9:30 instead of 10am?
Again, see how she goes on 1 nap. If you see though that things are heading towards the OT state.. that is, she is waking earlier and earlier for the day or that she is waking at night, then put her back on 2 naps for a little longer
Sorry for all the rambling. Hope I didn't confuse you
Let me know how you are going & if you have any other q's
Layla