how come she's not one of the female choices in the game?

Because she's a fucking dyke-cunt.

was her personality that bad?

She is a bitch for the first half of the game, but you do deserve it. The player in the game is a 100% pure loser. She's just protecting her friend from you.

i see, but i don't understand why they didn't bother to make her one of the girls you could pick though. personality aside she could have developed into a good character, and become a nice choice for the girl the main character ends up with.

Three girls with big tits and big asses is probably not necessary.

She doesn't like you, and it'd be a large betrayal of her best friend to go out with you anyway.

for it's intended purpose i don't think theres really need for a limit. but it can see what your saying though but it's not like that train of thought would be set in stone though. School Days showed a some what similar situation, and it was worked out into a possible route.