I'd say that's fine
Just listen to her - if you pick her up because she seems tired and she wants to get back down, then she's fine to keep going. These little dogs have TONS of energy and as long as they're a good weight and healthy, they can go and go and go, it's amazing
I usually walk with Alice and my other two dogs for about 1/2 hour (I walk pretty fast, but not sure how far that would be), but sometimes it's more like and hour and she's always fine, just drinks a bunch of water when we get home and takes a nap (sometimes she'll actually play for a while
).