I once had a girlfriend that actually attempted suicide. She regretted immediately though and was admitted to a hospital. I remember feeling like you though. Our relationship didn't last much longer, I was not old or mature enough to know what to do in that situation so I sort of just broke down. Looking back at that now, I should of course have acted differently. I think the most important thing you can do is talk it through with her. Of course the memory will still always be with you, but you can try putting the memory to rest by talking to her and making sure that she has no intent to actually take her own life. If you assure yourself it's not going to happen, you should hopefully be able to sleep peacefully. That's what I do in situations like these, hopefully you can use this for something