Try dry fire practice (with snap caps or dummy rounds of some sort).
Some good tricks that have worked for me have been doing at least 70 repetitions of DFP each night, dry fire (30 with laser, 30 with iron sights, 10 with left hand only either laser or iron) concentrating on a smooth pull. My carry gun has about an 8 pound trigger and LONG, so I find it necessary...but even if your gun has a crisp light trigger dry fire will help.
I think limp wristing is a bit like flinching in that the shooter loses concentration because she is anticipating recoil. Get rid of that mindset by shooting with no recoil and emphasizing a stiff wrist.
It could potentially be a gun fit issue, maybe the grip angle is weird (although this would merely be highlighted by the limpwristing issue - it doesn't mean she shouldn't be able to stop the limpwristing).
Another good trick for me to get into the proper training mindset is to do my smooth dryfire practice, 10-20 reps before shooting live fire. Focus on breathing and relaxation during the dry fire and live fire also.
Hope that helped!