EDIT : Yes I'm well aware that the Hasbro crew went a different direction with Cadence's back story. I don't need any more fucking lectures about it. I'm sick of explaining that I came up with these ideas before any of that info came out.
And that's why she wasn't invited to the Royal Wedding.
Actually she and her parents weren't invited because they would have sniffed Chrysalis out in a heartbeat, and Hedone's not sorry she missed it. She'd rather be clubbing or perfecting her vocal skills.
Just a head-canon fill-in for those who are new to watching me: I fit Cadence into the Alicorn Pantheon as Eros and Psyche's second daughter. Their first daughter is Hedone, a card-carrying legitimate member of the old Greek Pantheon.
MLP:FiM (c) Hasbro
Pony Hedone (c) me