I think you missed the original story. The flight attendant didn't ask her to cover her breast (which wasn't exposed.) She wanted her to put the blanket over her baby's head.
Personally, I would have accepted the blanket, said "Thank you very much," and put it under my baby's bottom. However, she merely declined it. The flight attendant's response (putting her off the flight) was un-called-for, which the airline itself acknowledged by apologizing to the couple and discipining the FA.
This information is for the benefit of those who are interested in an accurate story, rather than just another opportunity to demean and ridicule nursing mothers.