Let her take lessons. Trust me, she will resent you for pushing her to do things correctly, in a way she never would with a swing coach.
Teach her the bare basics. Grip, stance, posture, let her learn the rest as she goes along, and give her advice, only when she asks for it.
Yes Man you are so RIGHT. LISTEN TO APOC G10'S ADVICE. ONLY GIVE ADVICE WHEN SHE ASKS FOR IT. IF YOU ARE TO SERIOUS, IT TAKES THE FUN OUT OF GOLF FOR HER AND SHE WILL NOT WANT TO PLAY WITH YOU ANYMORE.