So, what about your friend? Is that still up in the air, or do you have a definitive answer as to what she told you?
What you witnessed in this situation, actually were a part of, is scary and overwhelming. You most definitely should talk to a professional about it, and seek some help, answers, and perhaps closure, for yourself. If you don't, you're likely to continue to mentally re-live this for quite some time, and this can take a toll on you. I have experienced something very similar, having to rush a loved one, very dear to me, to an emergency room, after she ingested an overdose of pills, in a desperate call for help. It is scary, and I was helpless to do anything, which to me, as a man, is a foreign concept that I have a difficult time accepting. But I needed answers. The answers, from a professional, and patience, helped. I hope you seek help from a professional, someone you can give all the details to, and who can safely help you decipher them, and get you to a place where you can move forward to more healthy relationships. My heart goes out to you, and to Sara. Take care.