Tendler began work as a hairstylist and makeup artist in New York City. In December 2007, she started The Daily Face on Tumblr. From there, she joined with MTV Style on various styling segments. Her tutorials have been featured in magazines from Glamour to HelloGiggles.

On July 5, 2014, Tendler married comedian John Mulaney at the Onteora Mountain House in Boiceville, New York. Their friend, actor Dan Levy, officiated the ceremony.

In a series of tweets on October 11, 2017, she spoke out about being groped by Ben Affleck in 2014, writing, “I would also love to get an apology from Ben Affleck who grabbed my ass at a Golden Globes party in 2014”.

In 2018, Tendler won critical and social media praise for her brief appearance in an episode of Comedians in Cars Getting Coffee. Critics from Vulture, New York Magazine, and The Decider, described her appearance as a highlight in the episode, in which Jerry Seinfeld buys Tendler’s husband John Mulaney a flat-weave wool entryway rug. Upon them presenting her with the gift, Tendler declines quipping, “You both like this one?”, to which New York Magazine declared, “Tendler won John Mulaney’s episode with a look.”

In 2019, Tendler appeared as a cameo alongside her husband in a party scene for the children’s musical comedy special, John Mulaney & the Sack Lunch Bunch.