Buckles, I am so sorry. It in essence is a death of loved one, the hopes and dreams, it all comes crashing down so heavy.
In my case 8 years ago I found out my STBXWH had cheated, we falsely reconciled, post-nuptial signed (thought it would keep him from cheating) now 8 years later, he's cheated again.
This time he filed the divorce before I could--strangely he wears that like a badge of honor, several times saying "that's why I filled"..he only filled because he was about to be exposed again for cheating and didn't want the post-nuptial to take affect with infidelity clause.
Its all very hard, but her mental health issues are not YOUR burden to bare. Mine too has a host of mental health issues which I felt were fixable, but I firmly believe some of us are "fixers" of people and think they can be good partners just if they were to get help.
I had to tell myself that these broken people are adults, help is available and even widely accepted and if they don't choose help why should we as the healthy people be subjected to their choice to not get help?
I have made so many excuses for my STBXH, his childhood, his eating disorder, even had it mandated in our post-nuptial for him to get therapy to which he went a handful of times and claimed he had PTSD from childhood abuse and he's now "cured"!!
All along I was damaging myself for being intertwined with a mentally ill person who did not care he was taking me along for the dysfunction ride. After years of this, now I need therapy for "feeling sorry & thinking he was fixable".
We are good people that look for the good in others, that's a incredible gift but it's often at our demise.