So you admit that Diana slept around? That makes her a whore. The circumstances don't matter. Just because Prince Charles was a jerk doesn't give her the right to commit adultery against him. If he commited adultery against her first she should have divorced him before messing around with someone else. Since she didn't that makes her a whore.
No judgement involved, just facts and definitions
Charles married Dianan and then contunued with his affair with Camilla. Charles was the whore(first) he married Diana because it was convenient.