I bet she's playing you.
When I first started walking my Hershey to the park, I had him sit every time we came to a street crossing. "Sit." Pretty soon, he was periodically sitting on our walk for no reason at all....didn't quite get the intended concept.
With these two, we just wait a second (or sit if there's actually traffic to wait out) "Wait."/"Sit." and then "Let's Cross". Of course, now, even if I don't have a dog with me, I think "Let's Cross" every time I cross the street. Do I get a treat?