This is a tough stage! I have a similar problem with my son. He love love LOVES his nap. And will nap 2.5-3 hours if we let him. That pushes bedtime pretty late as well (9 pm usually). In our family, we prefer the long nap and the late bedtime because I work at home, but only when my son sleeps. The late bedtime leads to a late wake up, which is nice for me because I get a good 3-4 hours to work in the morning!
If the late bedtime isn't OK for you, you're probably going to have to keep going as you are: shortening nap and then having cuddles to help her get over her grogginess. since that's her natural rhythm, you'll probably just have to put up with the groggies -- we have the same response when Owen is woken earlier than 2 hours from a nap.
This is probably a relatively short lived stage. She will probably shorten her nap on her own at some point. Or, she'll adapt to the shorter nap the more often you wake her.
No pretty answer to this dilemma I'm afraid!