Just something I would point out, Cadence was a Pegasus as a filly. It was in one of the books, but that is a small detail and really does not matter. Anyway, looks nice and would so cuddle her! It looks well done and tit looks is fantastic overall! Originality, I would say it is not that original since it is MLP, but honestly I am not here to judge because I love ponies! The crown looks nice, the eyes look amazing. The Mane and tail look alright as I can see and the horn looks a little floppy, but minor detail there. Overall this is good and I hope you continue to make great work!
Don't expect her to know all these things. Imagine how busy she is working on all these commissions and stuff, so she probably doesn't get to do things like read My Little Pony books very often. Just appreciate how awesome it is, even if it's inaccurate.