Tech billionaire turned party girl, 32, plans to sue her TV star ex-girlfriend after lurid sex and drug claims she says are false, court papers show

Published: 16:47 GMT, 11 November 2026 | Updated: 21:12 GMT, 11 November 2026

An ultra-rich tech investor turned DJ says she is preparing to sue for defamation after her TV star ex-girlfriend made a series of shocking claims during their break-up, court papers have revealed.

Lucy Guo, a 32-year-old AI entrepreneur who was once lauded as the world’s youngest self-made female billionaire, said she planned to take legal action against the British actress Wallis Day, 32, in a declaration made to a federal court.

Details of the couple's spectacularly messy split emerged in a petition Guo made to the United States District Court for the Northern District of California to enable her to subpoena Instagram owner Meta .

The eccentric Scale AI co-founder is seeking information about the reach of a post that she said Day, who has 425,000 followers, made on Instagram. In her declaration, she claimed the post was defamatory and that she intended to bring a lawsuit against Day in the UK courts.

The declaration stated: 'Guo posted an Instagram story to publicize and promote her latest single/remix titled “Done with your ex,” along with the caption, “fun fact: I broke up with my ex the night we made this".

The declaration claims that Day, who starred in the CW TV show Batwoman, reposted Guo's remarks and added the caption: 'Broke up with me lol…tried to get me to sign a prenup, came in wasted and tried to have sex, I told you no & left. Then stole hundreds of thousands worth of my belongings to coerce me into signing an NDA with hush money. I refused.'

The court filings said the caption continued: 'Because everyone should know how dangerous Lucy Guo is. But continue your narrative. Everyone knows the truth. Watch out guys, this person refused to let emergency services into their house when someone was dying because they had drugs everywhere #narcissist.'

In her declaration, Guo denied the accusations allegedly made against her, describing Day’s Instagram story as ‘replete with falsehoods’. In a statement to Daily Mail she said: 'I categorically deny these allegations. They are false, deeply damaging, and do not reflect what occurred.

Lucy Guo, a 32-year-old AI entrepreneur who was once lauded as the world’s youngest self-made female billionaire, said she planned to take legal action against her ex, according to court filings

Wallis Day, who starred in the CW TV show Batwoman and has 425,000 followers, is accused of sharing a defamatory post to Instagram, according to court filings

Included in the court filings is an apparent screenshot of a post that Guo alleges Day shared after their relationship imploded. Guo denies the claims made in the post and says in the declaration it is the basis of a defamation suit she is planning to file

'My legal team is addressing this matter through the appropriate channels, and I intend to vigorously defend my reputation,' the statement continued. 'Any suggestion that the current US proceedings are irrelevant is misplaced; they are a legitimate and necessary means of obtaining information directly relevant to the intended UK claim.'

In the court filings, Guo, who according to Forbes is worth $1.5billion, described the allegation about emergency services in the court filings as the ‘most offensive statement, which is entirely false’.

‘I never refused to let emergency services into my house to help anyone, let alone when someone was dying,’ Guo said in the filing.

Her legal offensive comes after what she describes as an acrimonious end to the relationship.

According to Guo’s court documents, the pair began dating in July 2025, before she ended the relationship in February 2026.

‘Thereafter, Day sought, unsuccessfully, to obtain hundreds of thousands of dollars from me,’ Guo alleged in the documents.

Guo is seeking the ability to demand that Meta hand over a digital paper trail that could help her establish the extent to which she could be entitled to damages from the post should a court rule in her favor.

Court documents reveal that Guo is requesting permission for a subpoena seeking 18 categories of information from Meta, including the identity and location of people who viewed Day’s Instagram story

According to the court papers she also wants the tech giant to disclose when the post was uploaded and removed, who was able to access it, and how many times it was viewed

Forbes estimates Guo's net worth to be $1.5billion. The bulk of her fortune came from a stake in the data company Scale AI, which she co-founded

Her subpoena seeks information about when Day’s story was uploaded and removed, who was permitted to see it, and how many times it was viewed, liked, shared and reposted.

According to the declaration, she is also seeking information about the follower counts of both women before and after the publication.

The location data could be particularly important because Guo says she intends to pursue a defamation claim in Britain, where the number of people who viewed an allegedly defamatory statement can be relevant to establishing whether it caused serious harm to a person’s reputation.

The application was made ex parte, meaning a judge could consider it without Day’s lawyers being present to challenge the request.

That has raised questions among legal observers, particularly because the two sides are already represented and have been exchanging correspondence.

Santa Clara University law professor Eric Goldman suggested that Day’s legal team could be ‘blindsided’ by the development.

‘Doing an ex parte proceeding when you know the other side has lawyers involved is just not great,’ he said. ‘It might be proper, but it still is uncomfortable.’

Raised in Fremont, California, Guo taught herself to code as a child and later dropped out of Carnegie Mellon University to accept a $100,000 Peter Thiel fellowship

Day attended the Sylvia Young Theatre School and the Arts Educational Schools in London before finding fame on shows including the DC Comics show Krypton

Guo is an unapologetic nightlife enthusiast who once boasted that there was nothing to stop her simultaneously being a CEO, an investor and DJing until 2am

He warned that without the opposing lawyers there to argue that the requests were too broad, a judge might ‘just gloss over’ the scope of the application.

Guo’s lawyers at Los Angeles firm Kinsella Holley Iser Kump Steinsapir have described their requests as ‘narrowly tailored’.

There is also a significant legal difference between the defamation laws in the United States and Britain.

In America, a public figure such as Guo would generally have to prove that Day acted with 'actual malice,' meaning she knew the statements were false or published them with reckless disregard for the truth.

British law is considerably more favorable to claimants in this respect, with the defendant generally having to establish the truth of an allegedly defamatory statement if relying on the statutory defense of truth.

Guo has recruited prominent British solicitor Paul Tweed, who says he has been involved in several hundred high-profile defamation cases.

No substantive UK lawsuit had been filed at the time of the American court application.

The dispute marks the latest extraordinary turn of events for Guo, whose rise through Silicon Valley has been anything but conventional.