As parts get old they collect grit and wear a bit. You've dealt with almost all the easy points, cables/housing, pivots, cable guides. But what first stood out is the lack of shift pod lubing. I suspect that with the cable disconnected from the der but held in your hand you'll be able to move the shifter through it's range easily. Is this the same if you're tugging on the cable with some real effort? Like the der return spring does? I wonder in internal friction in the shifter is adding the resistance your wife feels. BTW do you also feel the greater effort to throw the lever during riding? Andy.