At 20 months and then again at 3 1/2!!
I moved my dd into her own bed in her own room at 20 months. She slept in there for a few months but then eventually, after a few months, she was back in bed with me! I think she liked the newness of the room and pretty bed. So she's been sleeping with me until about a month ago when I moved her pretty bed into my room and now she sleeps there. I still have to lay down with her and have spent some uncomfortable hours in the twin crammed against the bedrail (since I usually fall asleep with her) but eventually she'll go to bed on her own. I'm not too concerned about it.
I think you shouldn't be too concerned about when other people do it. I slept with my daughter until over the age of three. Others co-sleep much longer. It's really what works for you and your family. My dd doesn't want to sleep alone in a room so I turned her bedroom into a playroom and office. Works great for us. I don't have privacy issues as I'm single and not dating.
As for when she's old enough is an individual decision. IMHO, I would start her out in her own bed in your room before putting her in a room by herself. Don't stress about this. Do what feels right to you!
Lisa mom to Gillian (7) : and three : :