Unfortunately people think once you train a horse, the work is done. Unfortunately not all horses are wired that way, and it can too challenging for someone that was just 'looking to ride.'
Most when they get a horse don't realize the work you put into it. Ground work, handling, feeding, fixing holes that arise, pasture management, reinforcing your leadership, riding so you don't create habits, etc.
Sometimes the best thing to do is say "My horse and I have worked hard to keep our working-relationship strong. It hasn't been easy but I deal with problems as they arise"
Just give them something to ponder over. If they want specific help, then they need to ask for it. If not, leave them alone. Seem helpful but not spewing information.
"Strength is the ability to use a muscle without tension"