I'm sorry to hear about your unfortunate situation. You can't really control those women's actions or feelings.
Your friend was probably right when he said that these women view as "competition" (although they should be happy to have more Greeks regardless).
I definately wouldn't reciprocate w/ the attitude and unfriendliness. Don't go out of your way to be super-nice-best-friends with these girls (you know what I mean), but do continue to smile, approach, etc. the women. They may just need to adjust to your presence on campus. And if you continue being friendly and showing love to ALL of the Greeks, they will hopefully begin to accept you there.
Also, when/if you implement any of the service projects or such that were mentioned previously in this thread, make sure to include them when you're inviting the other orgs. I wouldn't be surprised if they chose not to participate, but continue to be inclusive.
Also, maybe when they realize that the other Latina (and other) orgs are showing you love, they'll relax a bit.
Good luck, but don't stress about what you can't control
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SilverTurtle@greekchat.com
Phi Beta Fraternity
Phi chapter