Hi
guitar_girl,
During those five years that the two of you have been friends with each other, she must have displayed a certain penchant for dating interests in either sex – if you are clear about this information at least, it could be a good start for learning about what to do or not in your situation.
I agree with Sera on learning of her opinion about lesbianism. When she says that it's gross, is she thinking in terms of a love or sexual relationship between girls or is it something else that repulses her? If you clarify this issue as well, it would help you move forward in the sense that attitudes about lesbianism, whether positive or negative, do not necessarily predict how a person shall react towards it in reality. She's your best friend

... and you remain the person who is best placed for knowing how she could behave upon learning that you are in love with her. It will depend on the solidity of your relationship.
But as you've also expressed your fears of being exiled or made fun of in the community you live in, it becomes indispensable to create a network on which you can rely on if there is any problem of that sort.
Keep up with the courage and good luck,
Vi'