S.K.
I'd start reducing the morning nap. - by reducing the morning nap she also may be ready to go down in the afternoon earlier too....until she's used to 1 nap - once the morning nap is gone the afternoon nap might be a little later and longer.
my son is 20 mos since about 15 mos we've been down to 1 nap - he wakes around 7:30, naps 12-2 or 1-3, then he's in bed between 7:30 & 8. sometimes he does seem ready for a nap around 11 ish... but i stretch him (play /distract him) as long as i can - to get him to 12/12:30ish.