From HuffPost:

Rep. Blaine Luetkemeyer (R-Mo.) made the comments during a panel discussion at an American Bankers Association conference Wednesday. According to Politico, Luetkemeyer said people needed to “find a way to neuter” Warren, whom he called the "Darth Vader of the financial services world."

Latching on to the Star Wars reference, she responded:

"My first thought was Really? I've always seen myself more as a Princess Leia-type (as a senator and Resistance general who, unlike the guys, is never even remotely tempted by the dark side). Clearly the Force is not strong with Congressman Luetkemeyer (maybe he's a Trekkie)."

Here’s video of her appearance on All In with Chris Hayes: