Credit: Dan MacMedan/WireImage; Noel Vasquez/Getty Images

Lady Gaga and Brandi Glanville have each known a feud or two (or a dozen!) in their time -- but are the pop singer and reality star now in a beef with one another? While her Real Housewives of Beverly Hills costars (plus Andy Cohen) make trippy cameos in Gaga's just-released "G.U.Y." video, Glanville, 41, is noticeably absent -- so is another housewife, newbie Joyce Giraud.

So why did the Bravo starlets miss out on the chance to share screen time with pop music royalty alongside Lisa Vanderpump, Kim and Kyle Richards, Carlton Gebbia and Yolanda Foster?

For Glanville's part, there was no drama with the other women or with Gaga, 25: Eddie Cibrian's outspoken ex-wife was simply already booked! While the other women were filming at the famed Hearst Castle in California in mid-February, the former model was promoting her second book, Drinking and Dating, in NYC. (One of her pit stops in the Big Apple, in fact, was at Us Weekly's headquarters for an extended video interview!)

But Giraud, 38, made a conscious choice to skip the zany shoot. "Joyce chose not to do the video," a source close to Giraud, age, tells Us Weekly. "She didn't want to. She was asked, but it was after the reunion and Joyce was over it." (Indeed, the three-part RHOBH reunion, with part two getting underway tonight, March 24, was a typically epic, emotional affair.)

Tell Us: What did you think of the Gaga clip?