Laughing at the idea of her friend having an affair with Harold is to say he's undesirable, sweaty, stoned and likely not very virile. Basically a scrag-end of mutton.
But he's royal

so she's hanging onto him for dear life because she's even more of a scrag-end of mutton than he is. She's a criminal with no redeeming features, but is livid he's got that royal edge and always will have. She's done her best to snuff out his manhood and steal his royal mantle, but his feeble flicker endures and eludes her.
She's very confident and sure of herself despite all the setbacks and ridicule, confident enough to humiliate, henpeck, cuckhold and manhandle him in public. She's a seriously disturbed woman, the king's DiL. What a strange situation

.