Stim amount should be dictated by her stim tolerance and preferences, not the fact that she's a woman. There's not really much difference in what OTC fat burners women should use versus what men should use...a good burner for guys will work well for girls too.
If she's interested in Cardarine but wants something more natural, then look into Sup3r-Shred. Like Cardarine, it's a PPAR-Delta agonist, and also similar to Cardarine, it has endurance benefits. However, it is naturally occurring and considered "safer."
If it were *me,* speaking as a 32 year old woman who is within 10lbs of your wife's bodyweight, I'd stack Assass1nate + either Ignit3 or Bloodshr3d Raw. Probably BSR given that Assass1nate is already pretty comprehensive, and appetite suppression is a big thing for me when I'm dieting. Assass1nate is a non-stim burner + GDA, and Bloodshr3d and Ignit3 are both stimmed burners (Ignit3 is the more comprehensive of the two, and Bloodshr3d is better for energy and appetite suppression, IMO). Obviously you could run just one, you don't have to stack, they're efficacious on their own too.