M.M.
Let me ask you something: do you have a routine that you do every night with her? My daughter had a terrible time settling down, but once we established a routine that we did the same way every night,she accepted that it was bedtime and went down with no trouble.
What worked for me: brush teeth and go potty,get in bed and Mommy reads a story. Talk a little bit about the day, hug and kiss goodnight, give her her tiger to sleep with and lights out. What also helped when she was smaller was investing in a portable CD player and putting on soothing classical music when it was lights out time. Baby Einstein makes some wonderful CD's with nice music for sleeping - you can probably pick one up at Amazon pretty cheaply.
If she got up (and she did, at first), I simply put her back to bed and told her it was sleep time now. No anger. And I had to put her back, at first, about 3 or 4 times. It took a week to get her into the routine, but she took to it.
good luck and let us know how you do - establishing a daily routine may really help though.