Happy, I am not talking out of my arse either. There are a lot of children in other cultures who do not see their birth mother at all, for several years. The birth mother is working in another city/country, and the children are bought up by an amalgam of grandparents, uncles, aunts etc. with care takers changing depending on requirements within each household (e.g. At aunts for a month, another uncle for two etc.)
In situations where the husband has many wives, childcare may be delegated to different wives on different days, for all children.
Where extended families stay together, the family/child rearing tasks may be divided, with one aunt taking care of cooking and feeding, another of putting the children to sleep etc. As children get older, they may start taking childcare responsibilities.
A lot of women who work in other cultures, do not have the luxury to pay attention to their children cries or make a fuss over them. These children do go on to be normal.
Does that mean all these children are fucked up because they do not have a 'traditional' family structure, where there is one go-to person who fusses over them?
Attachment theory comes from a 1960s, middle class western notion of an ideal family with mum focused on kids. Fluid, multiple attachments is not a key part of this type of family structure. Doesn't mean it is wrong or unhealthy for the child who grows up in this environment (ok, some may be fucked up, but you find these type of kids in every type of upbringing)
In A's case, making the nanny speak in English to the child and trying to create a distance between the nanny and child, so that the child bonds only with new mum, IMO, is wrong and not necessarily to the benefit of the child.