Kat Von D bustled onto the set of “The Joy Behar Show” Wednesday with a huge diamond rock on her ring finger — but it was never mentioned on-air. The tattoo artist and TLC reality star confirmed her relation ship with Jesse James but refused to talk about if she’s en gaged to Sandra Bullock‘s ex, according to a source on-set. Before the show, “she told Joy very emphatically she did not want to talk about it,” our spy said. “Joy asked some Jesse questions, just not about the ring.” When Behar prodded into the relationship on-air, Kat replied, “Yeah, we’re a couple.” But when Behar followed up with more questions, she threw up her hands and snipped, “Why? . . . I just figured by now ev eryone would be tired of talking about it, it’s so old and boring.” Reps for Kat and James didn’t get back to us.