Is she sort of new?
Are you better than her? Do you have superior technique? I mean, if somebody isn't as good as you, you sort of spar at their level, right? You don't give them all you have. Otherwise you are just embarassing them and not helping them learn, right?
If this is the case and you are sparring at her level, stop that. Whatever strength you remove, replace with something else. Frustrate her. She'll end up wanting to use strength.
If not, if she's been there a while and has the technique, give up. She's made it this far being a wuss and will resist change. Lost cause.
He who establishes his argument by noise and command shows that his reason is weak. - Montaigne