Soda's Bad, Right?

I’m a hip hop dance teacher. I used to drink nothing but soda, period, at least two cans per meal even, and If I went out to dinner, and this can be backed up by anyone that’s had dinner with me, the waiters start bringing me two Dr. pepper or Pepsi at a time. I decided for a month to try just cutting soda, for a week and only drink it on the weekend, and only at dinner, and only one glass, or can, or bottle or whatever (it’s been very hard honestly). I’ve had my fiancee try the same thing with me (for her the craving is worse and she’s not half the soda drinker I am). Well after two months, I feel amazing, this may be due to the increase in water (literally haven’t had but a few sips a year, no joke, but now about two bottles a day and juice for flavor). I feel lighter, like I’m not so weighed down, and my stomach feels better (used to feel gross when I’d work out or dance). I’ve also noticed my stomach getting flatter. Now that’s my experience as a very active, male who’s had soda for years with little water. My fiancee on the other hand, well, she still feels heavy, hasn’t lost any weight (not that she needs to at all but for the sake of this info, she hasn’t) and she was actually better than me, water was always her drink of choice with only a few sodas a week, none some weeks. Anyone know why not drinking soda has been my miracle cure but actually had no effect or good change in her. She’s also not very active, she has a sit down job, but when she’s at home being mom to our son she’s always carrying him, putting clothes in the wash and picking up here and there, so she’s not a couch potatoe either? Just wonderin