I reread the epilogue and there are other's like Boo who are becoming Draconequi. However, I'm going to have to put a big red X to Boo becoming Eris. Boo is Boo, and like the other Brood her form will stop changing when she feels comfortable. Boo had a chance to become like Discord, so did Blackjack for that matter and they both turned him down. Boo wants to be like her mother, so in my opinion her physical form will still be pony-like even when Boo does become a Draconequi. Also she'll also have some of Blackjack's physical characteristics. I mean she already got Blackjack's libido, getting a red stripe through her mane doesn't sound so out there.