Affair discovered

[STH17]

Well no letter writing tonight because I was worried W's depression was heading towards suicidal. She came home from her workout and laid on the front lawn motionless staring at the sky for twenty minutes, then came inside and sobbed in the shower. Heard water sloshing so followed S4 into the bathroom. She was lying in the tub with her clothes on, but tub was drained, my worst fears not realized. Got son in bed, then went back to be with her. Told her I knew I wasn't the person she wanted to talk to, but could I get someone on the phone for her? She said nothing mattered. Eventually she got out and went to bed. I called a suicide hotline, first time I've done that. I checked up on her after that call and found she had dressed for bed but still depressed of course. It's hard to see her like this. She said I win, that I get to keep her as my bird in a cage. She feels utterly hopeless. What is detachment supposed to look like in this situation? I'm not a therapist and can't treat her depression, and at the same time to her I am triggering her depression now. I dunno any answers, so I'm writing this here and going to sleep.