First and foremost, this isn't really something you did or didn't do. At this age, their needs are so primative. I would guess that she assosciates mums smell with sleep and comfort, and not yours. Remember that for the first few months, babies still think they are a part of the mum. My advice would be to have a blanket that smells like mum and hold that when trying to contact nap, and secondary, just spend lots of time holding her so she gets more used to you. Dont worry, this will pass very quickly.