Preserving or forcing?

So a muslim girl, from an abusive family, is put in to foster care with a devout christian and later converts to christianity... The council take the foster mother off their register because

'They insist the foster mother failed in her duty to preserve the girl's original religion'.

So should the foster mother forced the girl to stay muslim against the girls wishes? When does preserving become forcing?

Sure, it was probably easier for the girl to convert while with a christian foster carer but that does not mean the foster carer caused the girl to convert.