"What's its name?" She's only giving Major half of her attention, having move to the edge of the treeline, watching carefully. Dogs don't generally just run. They run to something, from something, or because they want to play. The dog hadn't been scared, and nothing specific had drawn its attention. So it's playing. It wants to play. Which doesn't mean it won't get itself lost or hurt, it just means that it doesn't actually want the two of them to stop chasing it. They can work with that.

Might help if she has a name to call, though.