A Pattern to Fix

I'm working on my consistency of expectations and I've noticed a pattern that I want to fix. Today on our walk was a perfect example:

We were on in an isolated ravine, so I had dropped the leash and we were having a great walk. I see a dog and handler in the distance so I call Maya to me and pick up the leash. The handler says that his dog is aggressive, so we give them more room on the path, I tell Maya 'On By' and we pass by without incident except for the other dog barking and lunging a little. Maya does not react - great!

5 minutes later I've dropped the leash again and I can see the aggressive dog on the hill behind us. Maya stops and WATCHES closely. I tell Maya 'come' and get nothing so I go pick up the leash and flutter it until she turns her head and comes to me. I praise warmly and give her a treat and she immediately turns back to the dog on the hill and WATCHES. Rinse and repeat until the dog is out of sight.

Ultimately what I want is for that first 'come' to be responded to. I can keep doing what I'm doing, but I don't think that's getting us anywhere. I can ask for her to walk close to me after the initial head turn, and that will get us going again but it won't address the recall issue.

What's the best approach?