M.R.
Hi N.,
You didn't mention what her nap schedule is like. I would imagine that your daughter has just reached a point where her sleep pattern is changing. That happens every so often.
She may not be needing as much sleep. You could either try adjusting her bed time to a little bit later, or you could adjust her naps. You might want to limit a nap or eliminate one, especially if it is late in the day.
Also, just before bedtime, massaging the arms and legs helps to relax them. One way that kids keep themselves awake is through continued body movement. I found out with my son that if I could just get him lay still for even a minute or two, that he would fall asleep.
I really think that your daughter just doesn't need as much sleep, so you might consider adjusting sleep schedules a bit. Plus, as they learn more and get more excited about the world, they can have an interest in wanting to stay up to see it all. You're lucky that your daughter has been such a good sleeper. I'm sure just a little fine tuning will get you guys back on track.
Take care!
M.