I wonder why Megan's design is not very pretty.
Aside from the cliched "Beauty is in the eye of the beholder" argument?
Consider her role in the story versus the roles the other characters play.
Angela is "the firecracker." She's the shortest, the most petite, has the bright red hair, all leading to this impression of someone who is small but extremely "potent."
Hedwig stands out as "the bombshell." Tall. Blonde. Busty. She fits the classic stereotype to a T.
Melissa is "the vamp." (No, not "vampire," but related.) A "vamp" is, according to Merriam-Webster, "a woman who uses her charm or wiles to seduce and exploit men." And with the very fair skin, the dark hair and her little nose piercing, she looks the part. Again, your mileage may vary, but the idea is that she exudes an aura of the exotic which is what generates the majority of her appeal.
Leah is, not surprisingly, "the naughty nurse." That blend of caretaker - someone who'll literally take care of you. She'll fluff your pillow, get you a blanket, probably even make you dinner. And then, because she's a nymphomaniac, also shag you rotten on the floor of a public restroom.
And what's Megan's appeal? She's the "Plain Jane." The "Girl Next Door." That wholesome, good girl who you would take home to meet your mother. That paragon of virtue, of naivete, of innocence that some people will instantly jump to protect and others just want to corrupt. But she needs to look the part, too, and the pigtails and the relatively conservative mode of dress all ties into that.