For crying out loud! Is she supposed to hold a grudge against him forever because he hit someone who has since forgiven him? None of us know the situation, we only know what the media has told us about it. Clearly Rihanna has no bad blood with him, quite the opposite in fact so why should someone else remain incensed on her behalf?
She's at an event linked to her profession, if I refused to talk to everyone I didn't like or who had been a bit of an idiot at my work, things would be very difficult for everyone involved. Give her a break!