This is one of the reasons many suggest not allowing birds onto the shoulder. Your bird could be just showing affection because birds will preen each others facial feathers and rub beaks to show companionship. Since humans do not have feathered faces or beaks LOL this can result in biting the nose, plucking facial hair or nipping the cheek, lip, etc. It sounds like you are already working toward breaking her/him of this habit. If she likes being out then placing her back in her cage may be a deterrent. Also when she does nip, place her in a lower position (lap, couch seat or wherever is nearest and lower) and tell her a firm no. Repeat this any time she tries the nipping. Placing her in a lower position and saying a firm no (not hollering or showing excitement just a firm no) will show your dominant standing with her and should cause her to think twice about doing this again. Try not to show any exciteable behavior about the nip such as hollering, laughing, jumping around or she may see this as entertainment and do it again just to see the same reaction.