My 21 month old triplets (BBG) do this frequently as well. They are all still sleeping in the same room, so if one wakes up the others sometimes are awaken also. When they wake up it's hard to tell what's going on since we don't do the infrared video monitor thing. It's hard at times for us because one of our sons has hydrocephalus and if he cries excessively we have to check on him. Our other son suffers from IBS and night terrors and gets himself worked up into a sweat and needs to be calmed down, so I don't always get the luxury of ignoring them as much as I'd prefer to.
Then there is my daughter. She seems very similar to your daughter. She will occasionally wake up and be ready to play. She has toys in her crib to play with and she will babble and talk and play sometimes for hours. Sometimes she gets the other two up and playing also and I am often laughing at the sounds through the baby monitor, but I let them be. I figure it's only natural and as they get older they will do this less and less.
On the occasions that it a problem, I will bring her in bed with my wife and I, but she will rarely go back to sleep. She often plays "possum" and waits for awhile until she thinks I am sleeping and then she starts playing and yammering on again. She gets a prompt escort back to her own bed. She'll cry for a bit, but then she goes to sleep.
I don't think this is unusual and you sound like you've got a great plan and attitude toward it, you just have to ride it out I suppose. But I think you're doing great.
Good Luck!