Is there any way for me to save my friend?

If it were me, I would beat the shat out of jim and tell him if he makes her unhappy he will have trouble. But i have a short fuse with things concerning mistreatment of women, so that would probably not be the best option. I would have a heart to heart with kathy and ask her if this is truly what she wants, voice all of your concerns about their union, and then respect her final decision, for better or worse.