Meghan Markle was "fuming" when she saw Catherine playing the piano at Eurovision. The claim that Meghan was "fuming" is based on a single tweet from a user who has a history of posting negative stories about Meghan.
The tweet in question says that Meghan was "fuming" when she saw Catherine playing the piano at Eurovision. The tweet also says that Meghan was "jealous" of Catherine's talent.
However, there is no other evidence to support this claim. Meghan has not made any public statements about Catherine's piano playing, and there are no reports of her being upset about it.
It is more likely that Meghan was simply happy to see Catherine supporting Ukraine at Eurovision. Catherine's performance was well-received by the audience, and it is possible that Meghan was proud of her sister-in-law for using her platform to raise awareness for a good cause.
It is important to be aware of the fact that this claim is based on a single tweet from a user who has a history of posting negative stories about Meghan. The claim should not be taken seriously without further evidence.