My 4mo only really settles for me (mum). She will sit with dad and play but after 10 minutes she fusses until I come back to her. She's now started crying if people come up to her and smile except for me (her dad, grandparents who she sees regularly). I'm with her alone from 6am-7pm and we have a lovely relationship and are very closely bonded, but I'm worried I'm doing her a disservice by not 'sharing' her with others. Is this normal 4 month old behaviour, I thought separation anxiety didn't kick in until much later.