She has just given birth to a daughter, despite the fact that male births are preferred.

Do you have any data as to whether males are actually more successful than females? Traditional thinking in biology says that if you have a girl, there's an almost 100% chance that she will propagate the genes (i.e. have a child), but a male (especially in the past) has much less of a chance of doing that, and therefore having a girl is objectively (I mean biologically) the better outcome.