Labia come in all different shapes and sizes. What you're describing seems perfectly normal. I also have one that's larger than the other, most women do, and it isn't the result of a health problem and it hasn't interfered with my life in any way. If you're really concerned about it, mention it to your doctor next time you go for a physical.
You're friends seem to know what they're talking about, except for the one who says Gardisil gives you cancer. Gardisil does not give you cancer. Gardisil is not a vaccine against cancer, it's a vaccine for HPV. HPV can cause cancer, but it isn't cancer. It's a virus, like mono or the flu. When they say that Gardisil can help prevent cervical cancer, they mean that it can do so because it prevents HPV. Furthermore, your cervix is inside you and cervical cancer wouldn't cause one labia to be bigger than the other.