Apparently, because she thought that the comment was apparently a jab at Meghan allegedly not having a full family growing up. According to The Mail Online, Markle's half-sister Samantha hit-back at Prince Harry after his radio interview, where, he suggested that the Royals were "the family Meghan never had".
A comment, that uh, apparently didn't sit well with Markle's own family. The Mail notes that Samantha Markle took to Twitter to discuss the comments, even, going as far as to in detail discuss how Markle herself grew up.
Our household was very normal and when dad and Doria divorced, we all made it so it was like she had two houses.
'No one was estranged, she was just too busy.
'Meg's family (our family) is complete with sister, brother, aunts, uncles, cousins, and the ...