Why do you care about what others think about your situation so much? If any of them knew your wife they probably suspected that she had issues anyway, unless she was an expert at hiding them. My experience with bipolars and depressed people is that their condition is usually not hidden from outsiders, those who pay attention can spot the signs.
As to your other question, you can't force someone to stay married or committed to you or the relationship. If they want out, they will opt out. All you can do is be the best kind of spouse you can be. If they decide to leave, then that's their decision, as painful as it is.