My deepest sympathy to you, the family and friends. I can only imagine how you must be feeling.
A couple of years ago I was suicidal, but thankfully, I got the help that I desperately needed. All I can say is, your friend must have been in a very dark place and ending it all, was the only way out she could see.
Hopefully she's in a much brighter and peaceful place right now.
Hope you all get through this terrible time. Be strong!