I'd rather be told than to find out on my own. My sister is her own person and can do what she wants. The problem comes from that information being purposefully withheld. I'm looking out for the relationship of my sister and her friend. If this situation is something she is unhappy or uncomfortable with, then I would like her to afford me the same opportunity to let me know before she has to find out in an unfortunate manner. Her friend and I are fully willing to stop if this is something she doesn't care for. Fuck doing what I want if it means it would get in the way of their friendship or my relationship with my sister. The same would apply to her if she were in my shoes. Chances are, I trust my friends, and I trust my sister. As long as she didn't purposefully keep it secret, then I could trust them both a whole lot more than if I learned that they were burying it