Thanks Nekhbet. They are the kind of techniques the trainer will help me with, I expect. I am currently really bad at dealing with it when it happens. And I have been using trial and error to see if I could find a way to snap her out of it and clearly it resulted in too much error! I trust this trainer knows what she's talking about so will stick to the techniques she will demonstrate and hopefully being consistent will pay off.
ETA: And yes, she is not dog aggressive, just reactive. And even only mildly so. She doesn't show any signs of stress when leashed dogs pass or when we pass dogs behind fences, etc. We have 3 dogs we've never met in the yard behind us, always hanging around at the fence between the yards and her only reaction to them making noise is a sympathy whine or a wag of the tail. But that is why I want to nip this in the butt now and make very sure that it doesn't get worse. And I hope that I will learn how to prevent it from even getting to the point we're at now with future dogs or foster dogs.