An Upper East Side woman who believes a spurned suitor started an anonymous online smear campaign against her is suing the company that hosted the vile websites to unmask the person behind them, according to a new lawsuit.

Keila Landim De Souza, a Sotheby’s real estate broker, rebuffed Ginu Shaji’s advances after meeting him in 2016 while she was dating another man, according to a Manhattan Supreme Court lawsuit filed Monday.

Shaji then allegedly began “stalking” De Souza on various electronic platforms such as Snapchat, Facebook and email. He also contacted her friends and called her daughter to spread lies about her, the court papers charge.

“On one occasion, Mr. Shaji threatened to ‘destroy’ me,” De Souza said in an accompanying affidavit, noting the incident spurred her to obtain a restraining order against him.

Soon after, De Souza was notified that someone had begun anonymously posting lies about her as well as her photograph on websites including “shesahomewrecker.com,” “reportcheater.com” and “exposecheatersonline.com,” the court documents allege.

On reportcheater.com, a post that includes a photo of De Souza says, “Keila landi de souza destroyed my married life of 28 years…my husband met her at a restaurant in NY and they started seeing each other and onetime [sic] she recorded a sex video of her and my husband and blackmailed him for money and he refused and she then send me the video.”

“Upon information and belief, it was Mr. Shaji that posted defamatory information about me on the aforementioned websites,” the court papers allege.

These posts are especially harmful to De Souza’s reputation, since potential and current clients frequently do internet searches for De Souza, the court documents say.

De Souza wants Arizona-based company Domains By Proxy, LLC — the defendant in this case — to reveal the identity of the person who made the posts to confirm that it is Shaji.

She says she plans to sue Shaji for slander and defamation once she has more information.

Domains By Proxy declined to comment.

Contact information could not immediately be found for Shaji.

Additional reporting by Priscilla DeGregory