I suggest you continue asking your horse to come with you, without making an issue of it, but trying to increase the amount of disomfort your horse can tolerate. I don't mean riding her if she's limping; but she CAN learn to live with some discomfort. (As we age, I believe we all do! It's just one of those things.) The thing you're looking for is her feeling better at the END of a session than when starting out. She'll remember this.