This happened to me last night too, i had been trying and trying to get her to sleep, with no avail (i think thats the right word), so i just put her in her cot, and left her, thinking she would cry, but nope, she went to sleep. Tried it again this morning, and hey, it worked!! Tried it again this afternoon though, didnt og down so well, although i think there was a bit of noise around the house more than usual so she got a bit intrigued.
Congrats hun, i hope it stays this way for you, and for me too