Andi Dorfman warns Kaitlyn Bristowe about Nick Viall

Andi Dorfman thinks Kaitlyn Bristowe should avoid Nick Viall.

The 28-year-old season 10 Bachelorette appeared to tweet as much immediately after Viall showed up on this week's episode. Viall was the runner-up on Dorfman's season, and famously revealed he slept with the star on the After the Final Rose special.

"One word.... RUN! Okay two... RUN FAST! #TheBachelorette," Dorfman wrote. "Really wishing I had the superpower of reaching through my TV right now. #TheBachelorette." The warning was favorited over 6,600 times.

Bristowe and Viall exchanged flirty texts after the former appeared on season 19 of The Bachelor. The season 11 Bachelorette invited Viall to join the show Monday, much to the consternation of the other contestants.

Dorfman competed on season 18 of The Bachelor before The Bachelorette. She and Josh Murray got engaged on the season 10 finale, but ended their relationship in Jan. New episodes of Bristowe's season air Mondays at 8 p.m. ET.