Hilary Duff teases that Liza's big reveal isn't the only jaw-dropper of Younger Season 5

The moment Younger fans have been waiting for for four seasons has finally arrived: Liza’s (Sutton Foster) boss and love interest Charles (Peter Hermann) knows her real age.

On Tuesday night’s season premiere, Empirical Publishing owner Charles learned that Liza — who got hired as an assistant under the guise that she was 25 — is actually in her 40s.

“It’s huge,” Younger star Hilary Duff told PEOPLE of the reveal during the show’s New York City press day in April.

Though fans will have to wait until the next episode to find out how he reacts, Duff said the fallout is “scary for Kelsey,” her character.

“As much as she loves Liza, she’s worked really hard to get where she is and she continues to put her at risk,” the mom to 6-year-old son Luca continued. “I think she’s kind of sick of it. I don’t think Kelsey loves being a liar with Liza. It makes them look like frauds.”

With the secret getting out around the office, Kelsey doesn’t want her credibility to be questioned.

“She has on opportunity to kill it and not make too many mistakes and that would be a huge betrayal of a lot of people’s trust,” said Duff, who called out her neighbor on Instagram last month for smoking inside their New York City apartment building. “And it just seems like a psychotic thing to do, lying about your age by 20 years.”

But Duff said that unfortunately, “Everything’s going to come out.”

Kelsey might also consider leaving the publishing house, where she runs the successful Millennial imprint.

“She’s definitely considering it,” the former teen star teased. “You never know what Kelsey’s capable of. She’s a little bit of a wild card. As much as he wants to push ahead, I don’t think she’s above doing something that makes her really uncomfortable, like maybe leaving a job and having to work her way up again. She holds a lot of worth at the company though and they know that, so well see how far she gets with that.”

Younger airs Tuesday on TV Land at 10 p.m. ET.

This article originally appeared on PEOPLE.