If any of my friends who borrow my dogs to walk them EVER let them offleash I would beat that person within an inch of their life. Purely irresponsible to be letting another person's dog offleash. Rediculous.
You did the right thing. You weighed the pros and cons and as far as you were concerned the cons outweighed the pros and you kept him onleash. I have had people try to make me feel bad for keeping Wally on leash, like when we're walking on the beach, but I KNOW that if he was offleash and a horse ran by he would be gone, or if a small dog ran by, or a bird, he would be off like a shot. Don't let her make you feel guilty for doing the responsible thing.
"All changes, even the most longed for, have their melancholy; for what we leave behind us is a part of ourselves; we must die to one life before we can enter another." -Anatole France