W.I.
I have to say I agree with Tina. As hard as it might be, don't encourage the behavior by rewarding her with your attention.
I know you said you already have a routine. But here are some that work for us:
Prepare her in advance that bedtime is coming soon - we'll read these two books and then bedtime, okay, just one more book and then bedtime... Just keep talking about what she is going to do next until she goes to bed, to give her time to wrap her mind around the fact that bedtime is coming soon.
OR we do something we call TALK ABOUT DAY. When our son is in his bed, we talk about the day - who woke up first him or his brother, what did he eat for breakfast, did he have a friend over or go out somewhere, what did he have for lunch, did he color any pictures, did he get to play with Daddy before dinner, etc. I guess it started so my husband could hear what the boys did that day and just became part of our routine. But, it is something that our son looks forward to doing every night.
Does she have a special lovey? My son sleeps with his Pooh Bear(and puppy, elmo, lyon and sometimes barney - but mostly Pooh). Maybe take her to a Build A Bear workshop and make up a special bedtime friend with her. Let her know that this is HER SPECIAL FRIEND to sleep with her at night. I think they even have matching clothes, perhaps they have matching PJ's for her and the bear? If you make a big deal out of it, maybe she will want to sleep with her new friend?
The only other thing that my Dr. told me was that there are only two things a toddler can control - eating and sleeping. She said that he will eat and sleep eventually and I just needed to have more patience than my son and I will win the 'battle' in the end. He goes through his periods of trying to control his sleeping - either at night or naps. I just keep reinforcing that he needs his sleep - which he absolutly does!! and within days he is back to his schedule.
Good Luck J.