Like everyone says it's best to play it down, maybe ask them about it just to see how they react. I had constant thoughts for about a year and got hospitalized. Led to me being more attached to her and even trusting her more in other ways after it all. I was very open about them, but didn't know where to draw the line... The hospital was kinda traumatic and fears of returning seemed to have replaced the suicidal thoughts. But after the hospital and everything I actually was able to trust her more and think the therapeutic alliance is stronger. Though I'm not sure I could trust her or any therapist with my thoughts of suicide and wanting to die. Initially, I stayed with her because she already knew about them and if I saw someone new I'd probably never bring it up nor the hospital and wouldn't get much help.