For those talking about the cheating, Melissa mentions it's common knowledge, after all, Ian is sleeping with a ton of girls and Melissa kept attacking them, with guards coming in all the time to take her out.
But the prince turned it so that she's to blame for being so mean or clingy and everyone blames her for the constant cheating, it's not that the father and brother don't know, they know, every noble knows, they either don't care or think it's all her fault for being so mean.