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The second source adds that Kyle was going through a particularly difficult time while in the Hamptons, as her sister Kim Richards had just been arrested for allegedly shoplifting at Target, Kim's second arrest in four months.

Bethenny, who has known the Richards sisters for over 20 years, hasn't held back on Kim and Kyle's strained relationship in the past. While appearing on Watch What Happens Live this past April, she let Andy Cohen in on what she thought was the core issue between the siblings. "They're in a town where money and attention and fame are really prevalent, and I think it's like an alternative universe," she said. "They're living this, but then they're also living it in the press, on Instagram, on Twitter. It's a really really murky, and I don't know how they're going to get out of it. Being on television together… it doesn't seem like it's going in a good direction."

Bethenny's upcoming cameo won't be the first time the worlds of Beverly Hills and NYC have merged on Bravo. In season six of RHONY, Kristen Taekman and Carole Radziwill enjoyed a lunch with RHOBH stars—and real-life buddies—Brandi Glanville and Yolanda Foster.

Are you looking forward to a Bethenny appearance on RHOBH? Sound off in the comments below!

—Reporting by Beth Sobol

(E! and Bravo are both part of the NBCUniversal family.)