Persistance is the key hun. Make sure you continue to try it out during the day time too. Does she sleep in her own bed during the day ??

The 20 minute wake up is just her waking up after her sleep cycle. At her age the cycle is only about 20 to 40 minutes. Actually from memory close to 40 minutes. Does she go down to the cot awake ?? If she is already asleep and has been for abit of time then her sleep cycle could already be up. I had huge problems with trying to get Tehya to sleep through her sleep cycle. We ended up at sleep school. Obviously she didn't get much better but atleast now I know what I am talking about. LOL.

When she wakes up try not to pick her up, rather keep the room dark and try to resettle her, just patting her gently on the back until she starts to drift off. Now at sleep school we were told not to do it til they fall asleep because then when they awake again they can't put themselves back to sleep. Rather to just resettle them enough to be relaxed and then leave them to it again. That part is totally up to you. Well, it all is of course

Goodluck. Just thought I'd give you a few ideas. Do with them what you please