I have see the other post about this, but our situation is slightly different.
She is 2yr 4 months and she loves the big bed in her room. Its actually a bed, not a cot bed, and the frame is metal (I know we never realised!) so can't put a guard. Mother in law suggested a pilow on the side, she has 5 children and neither fell (I now think that probably she doesn't remeber). So in she went all happy (I put her in her sleeping bag because she still doesn't know how to cover herself with the duvet), put a pillow under the fitted sheet and she fell sleep instantly. At 1am I hear this thump! and went to her room and she was still sleep on the floor (first afternoon at nursery and she was shattered but she won't go everyday)! She seems to have rolled over the pillow on the side, so I put her back in the cot.
I'd love to leave her in the cot for a bit longer, but she demands to sleep in the big bed!
Any ideas will be greatly appreciated!!