I wonder if she would benefit from looking at the hole over the short putts?
Keep the usual routine for putts longer than, say, 9 feet or something, but look at the hole on the short ones.
Use a Pyramid putter or one of those lie-angle balanced putters for better line and more consistent speed.
She has likely already tried hypnosis. Maybe a hypnotist could give her a little trigger she could do right before a putt to give her confidence.
Problem with short putts is that you have to not care about them too much. Any putt that you care about too much becomes much harder. That's probably why she putts ok on the first three days but then reverts back to poor putting on the back nine on Sunday.
She has actually improved her putting a lot. She used to suck at putting all the time, but now she only sucks when it really counts.
