The stats are all in the range of possible stats for Clefairy, and it can learn Soft-Boiled in Fire Red and Leaf Green. It might be legitimate, but I’d need more information to know for sure.
Edit: Because it came from Alola, it isn’t possible for it to know Aromatherapy and Soft-Boiled at the same time. Aromatherapy is an egg move, which means a Clefairy (from gen 3), won’t be able to bred again with aromatherapy.
It can’t have Unaware as an ability either, so it is most certainly illegitimate.