Just make sure you are washing your hands before nappy changing, giving food etc. Don't share food or kiss her. Cold sores are dangerous to really tiny babies, but not one that old. I had a freak out when ds was 4 months old and I kissed him on the head before I realised I had one. I actually called 111, but they told me the big danger is only to newborns and avoid touching eyes, mouth and genitals.