Tegan, you should be able to pick up a second-hand bassinet for the baby at a cheap price on ebay or in a babygoods store, which will give you a few more months up your sleeve.
If you move Lily into a bed before she is ready for it, it will be hard persuading her to stay in it at night.

I agree that ideally you don't want to move her out of her cot and the baby straight in, she may well feel disposessed. When we moved our girls out of their cots into the beds, I made a bit of a production out of it and took the girls out to Spotlight to let them choose their own doona cover for the first night in the new bed to make it special for them.

Kerrie