OK, nap 1 hasn't lengthened yet, but I would expect her to take a few days and possibly more A time to get the longer nap.
Nap 2 is getting very hard to extend, leads me to think she's just not tired enough to get another cycle, but she needs it, leading to OT later.
She's been on quite a short A for some time if I remember rightly, so I am cautious to push up too quickly, her body clock needs to adjust. If you think she can take a little more than the 3hrs tomorrow then go for it, but if not just hover there for a couple of days and let her adapt to it, then up again.
I know those 10.5 - 11hr nights. DS was exactly the same until we dropped to 1 nap per day at 11 months. He now goes more like 12 - 13hrs per night and boy do I feel the benefit
Just hope it stays that way a while.