There are no least hurtful ways of breaking relationship. It is always difficult for both the people involved and not only for one who is being dumped. I think you need to find out right time, right place and right words for your break up. As she has tendency of harming herself, avoid evening or night time when she has long time to brood. If it is possible, inform another close friend about break up as well as your concern about her suicidal tendencies. Do not do it in a public place. Pain of breaking should also reflect in your words and attitude (even if you don’t feel it, fake it for her sake!), probably that will help her to accept the break up. Do not try to assure her that you can still remain a good friend; this is more hurting then soothing……… DETAILED ANSWER MAILED TO THE READER