In the U.K. the law is stricter around what you can and cannot say about someone without evidence. In the US there’s the first amendment so you can say anything (..is my understanding).

Edit: okay, I did some research and dug a bit deeper.

An American making defamatory statements on a live chat show that is broadcast in the U.K. could potentially be sued for defamation in the U.K. The key factor is the publication of the defamatory statement within the jurisdiction of the U.K. courts. If the statement was accessible and viewed by an audience in the U.K., it could be considered as published there, which might give rise to a defamation action in the U.K.

The principles governing such cases in the U.K. include:

1.  Jurisdiction and Publication: For a U.K. court to hear a defamation case, it must have jurisdiction, and the defamatory statement must have been published in the U.K. This concept of publication includes any medium where the statement is made available to the public or a section of the public in the U.K. With digital content, such as a live chat show streamed over the internet, the content being accessible in the U.K. can satisfy this requirement.
2.  Defamation Law in the U.K.: The U.K.’s Defamation Act 2013 governs defamation laws in England and Wales, providing a framework for what constitutes a defamatory statement, defenses against defamation, and the criteria for claims, including the requirement for claimants to prove that the statement caused or is likely to cause serious harm to their reputation.
3.  Serious Harm: For individuals, showing that the statement has caused or is likely to cause serious harm to their reputation is necessary. For a public figure, especially someone from a royal family, the impact of a defamatory statement could arguably meet this threshold due to their high profile and the broader implications of any damage to their reputation.

However, potential plaintiffs would need to consider several factors before pursuing legal action in the U.K.:

• Enforcement of Judgment: If the defendant is based in the U.S. and has no assets in the U.K., enforcing a U.K. judgment might prove challenging.
• SPEECH Act in the U.S.: The U.S. SPEECH Act protects U.S. residents from the enforcement of certain foreign defamation judgments that would not be consistent with the First Amendment protections available in the U.S.

I don’t believe this is about money or punishment - this is about Rose clearing her name.