Re: pricked by needle in nightclub
If the needle were infected with HIV, the chance of infection for your friend would be low, because HIV just isn't a really strong virus outside the body. However, if the needle were infected with Hepatitis B or C, the possibility of infection would be significant, because hepatitis is a very "strong" virus.
You might check out the CDC website. I'm not sure how much info they have about transmission, but I'd think they would have good info.
That said, I would try to convince your friend to get tested for HIV AND Hepatitis B and C. Let her know that she is probably negative for all, but on the tiny chance she isn't, it's better to know so she can get proper treatment as soon as possible. Go with her, and help her be strong. Knowing the truth is always better. I really feel for her and hope and pray she's okay.