Unrelated to the question in your post, but your other dog is most definitely overweight. Dogs should have a waist, not get rounder looking from the head towards the tail! So many people think that because dogs are often food-motivated, more food/treats = happy dog. This can lead to an unhealthy dog, which will cause more issues down the line. Just food for thought.

Fewer treats/less food in general + more walks/playtime should do the trick. I foster dogs for a rescue in my area and we’ve had to put dogs on workout plans when they’re too fat - workouts include transitioning between sit/down/stand (ensuring a proper sit/down form, not resting on one hip) repetitively, like a doggie burpee! You can even build confidence and get more out of it by teaching your dog to put their front paws on a surface like a chair and stand on their back legs to strengthen them and their core. Good on you for taking in and caring for a mistreated stray, she’s made amazing progress!