Velma syndrome

A girl with Velma syndrome is nerdy-looking, glasses-wearing, mid-length dark haired, and generally short and somewhat curvy.

She does not exuberate feminity nor is at the center of male attention, but she is still quite attractive (usually for reasons like her intelligence, more modest dressing-style, or her mild sense of humor rather that physical appearance).

She also has inopportune moments of vulnerability where she needs extra help, care, and attention (like when Velma looses her glasses).

Basically describes a girl similar to Velma from Scooby-Doo

A: "Hey that girl's kinda hot."
B: "Yeah, but she's got Velma syndrome. She's too modest and smart for you."
A: "You're right. I need a hoe like Daphne."