OK. She has already said she doesn't want you to meet this "friend." That's it right there. Of course she's allowed to have friends, but she is not allowed to have a special male friend who she talks to all the time and sees frequently, who you are not allowed to meet.
Don't call the guy. Don't call the relative. Don't hire a PI. What would be the point?
I hate to say it, but you screwed up the other day. You spent time with her, had great sex, slept over, and then what--you grilled her for leaving for work a half-hour early?
Your pursuit is what is pushing her away. If she ever does call you back, do not pursue. Don't question her. Let the word "whatever" become your new mantra.
