fairly obvious to me that she wasn't trying to insult anyone or disrespect grandpa. the comments about her son being born out of wedlock are cheap and easy and unkind and probably meaningless.
knowing him as i do (he's my adopted brother), i'm pretty sure 75th was having fun, but that doesn't mean it wasn't low class and (hopefully) beneath him. however, she is just slightly insane and will not easily let things go. the other side also likes to argue and stir shit up. maybe a slap fight is in order.