Even if her curls are gone, you can tell a Y3 Bow Tie by the length of her hair. Pull her mane tight around her neck under her chin. If it reaches almost all the way back to her hairline, she's a Y3, and if it stops somewhere under her cheek, she's a Y2.
My Y2 Bow Tie is also a darker, summer-sky blue compared to my Y3 who is more of a pastel, robin's egg color. But that might simply be due to internal variation, I'm not sure.