how old is the child? You use very emotive language in your post "hard working nurse" "unaccosted in the bosom of her family" etc, but of course, this is just yours and hers point of view. playing devil's advocate; You don't know for sure what is best for the child - perhaps knowing her dad IS best for her? and less likely to muck her up emotionally in the future rather than finding out at a later date that her family kept her from a relationship with her real dad? perhaps having a modicum of doubt over parentage is comforting for the husband, but will it be comforting to her in the future, not knowing? Also, this is obv someone close to you but don't forget, she chose to have a child with this man, it's not something that just happened! Ok so she clearly regrets it now, but she will be forever tied to him, no matter what country he is in. Perhaps the dad really has thought "i've been a crap dad, but i want to try making up for it now"
again, let me state i am playing devils advocate