Hi all -
Our 6.5mo has always been a great sleeper. The past couple months she’s been steadily on a 3 nap schedule and sleeping through the night without feeds, 7:30pm-6am. Her wake windows have been just 2-2.5h, and she always went down to naps easily. Just pop her into the crib and she’ll generally put herself to sleep. Her naps have been about 1-1.5h morning and noon, then a 30min cat nap around 4pm. Down for the night at 7:30.
So basically,
6:00am Up
8:15am first nap (1-1.5h)
~12:00 second nap (1-1.5h)
~4pm cat nap (30min)
7:30pm Bedtime
Suddenly this week she started fighting the last nap. Not just fighting, she just wouldn’t sleep at all. So we ended up with almost 5h wake window before bed time, even when making her bedtime one hour earlier than normal! (6:30) She was obviously too tired at that point but went down for the night without too much struggle.
I wanted to try & cut her morning nap short but today, she wouldn’t go down at her usual time despite rubbing her eyes and looking sleepy. Finally she fell asleep after 3hr awake, only when rocked to sleep.
I’m now clueless if I should let her sleep as long as she wants, then try a 2-nap schedule, or make the morning nap short (45min) and try to squeeze in a proper noon nap and the cat nap as before?
Until now she’s been visibly tired at that 2-2.5h mark and went to sleep herself within 5min of being put down to her crib. Could she really be ready to jump to 3+ hour wake windows and drop a nap so suddenly?
We have her shots this afternoon and I’m scared she won’t go down for her second nap before we need to head out and end up a wailing mess even before her shots! 
Thanks in advance for any tips!