I put my son in a queen sized bed at 17 months for that very reason. So dh could start a bedtime routine with him and lay down next to him to help him settle. He refused to go to bed for dh and it wasn't a good thing with number 2 on the way.
The only think you can do is try. What's the worst that can happen? If it doesn't work out you have a bed for when she will eventually need it anyway