She did know about their collab. together as she said "...Makin a song w/ the dude that beat your face off is not a good look"
referring to the song they recently made.
As for the insult she originally made, it's alot more subtle than the suggestion you made about the cake batter which would...
Really? Not a personal attack? Tell me how talking %##% about her getting abused by her ex is not personal
Yes, let us judge people by their tweets...
As far as I see it, rihanna is a person and people sometimes act on their feelings and not with their heads.