So I started seeing my best friends sister a little while ago. His girlfriend has a problem with it now, she didn't at first but now she hates the idea. She tells me that my buddy is not cool with it anymore either, but he tells me he Doesn't care and we can do what we want. Buddy's girlfriend and his sister are best friends but haven talked since we started seeing each other. She is now telling me she is going to break up with my buddy if we keep seeing each other because she Doesn't want to feel the way she feels about it anymore. I am also business partners with my buddy, I don't think much can come between me and buddy, but not sure. I really like his sister , but I don't know her that well. I do want to keep seeing her but not sure if I should , and I don't want to regret not seeing her... Anyone have any advise