If it isn't broken... don't fix it
!
Usually the signs when they're ready to go to 1 nap a day is refusing to go down for one of the naps (or both of them) or taking AGES to settle and go down. Another hint would be the nap be less than 1 hour and being cranky and whiny during the awake time.
In some other cases there are night wakings or super early mornings in the mix. If you don't recognize any of this sings, I'd recommend you to wait until she starts showing one of them and then we can come up with a plan.
Sounds to me that she's doing great! Congratulations!