Daryna is such a beautiful name. Dah REE nuh is the way I pronounce it. It’s a name I would consider using for a baby girl even though I’d worry about it always being mispronounced here in the USA.
Daryna is not diminutive, it's just a common Ukrainian secular form of saint's name Dariya. The other common secular form of Dariya is Odarka (Одарка, oh-DAHR-kah). [noted -ed]