My first thought on this would be OT as well - my 18-month old has a 2h+ nap, so 1.5h at 16 months seems a little light. Even if she has been okay on this routine for a few weeks, it could be accumulated OT from having a little bit less sleep than she needs every day, iyswim? Waking at 9 is also a sign of OT - could you maybe try an earlier bedtime for a couple of days to see if that helps?