Direct caloric burn, long term metabolism changes, etc. for a given activity vary based on the input fitness level of the person.

Calories in is the easiest levee to pull for rapid change as exercising enough for major direct calorie burn is challenging at the beginning. The biggest short term exercise impact is from activities that increase muscle mass as muscle takes calories to maintain thus boosting metabolism.

I will add that the walks were around an hour to two to get 10k steps and over 4 miles.

I challenge anyone to walk an extra ~25 miles a week with no diet change to see if they gain weight.

Pretty sure her daily walks did contribute significantly to her weight loss.

(I do apologize as my response was based on a science article that I read not too long ago but I cannot find it to substantiate my claim)