Any logical person will see that Rihanna has some bitchiness to her. Shes feisty. Do you see the way she talks on Twitter??? She knows how to drag, and call her fans 'stans" like any normal internet forum poster does. Ciara while I agree the tip insult was too out there. Its just a reflex. We all do stuff that we regret when we're angry. Not because you're a celebrity you are unable to be human.
But clearly her comment had nothing to do with what they were talking about.
I don't know maybe it's just me, but all Ciara said was "she wasn't the nicest". Whether it was random or not. I don't think it warranted embarrassing her publicly. What Rihanna said was really harsh.