Rachel Eck, in an interview with Buzzfeed, claimed that the actor "aggressively groped" her when she met him at a hotel in 2014.
Eck claims that the meeting with Westwick was set up by Australian film producer Kaine Harling, who is her ex- boyfriend.
Eck said that the 30-year-old star tried to kiss her and added his behaviour got worse further.
"As the night wore on, it got worse and he got more handsy," she said.
Eck said she confided in Harling about Westwick's behviour who asked her to stay as Westwick wants to apologise.
More From This Section
"I shoved him off as quickly as I could and left," she added.
Westwick was earlier accused of rape by Aurelie Wynn and Kristina Cohen, which he has both denied in a report saying, "It is disheartening and sad to me that as a result of two unverified and provably untrue social media claims, there are some in this environment who could ever conclude I have had anything to do with such vile and horrific conduct.
"I have absolutely not, and I am cooperating with the authorities so that they can clear my name as soon as possible.