As virtually every poster has noted, starting a new shooter on the dominant eye side is the preferred solution. While it may take longer initially to feel comfortable, once coordination and muscle memory take over through repetition of motion, it will be the only "natural" way for her to shoot. If she's hesitant to shoot from the opposite side, you should point out that the lead hand is what controls muzzle position and since she's now able to use her dominant right hand as the "pointer" it's actually not a handicap at all.
On the other hand (no pun intended) some people can never get comfortable switching sides. Then follow eightbore's comments about using an opaque dot positioned so that only the muzzle is blocked when the gun is mounted to face. Too large a dot, or one that is any way obtrusive to seeing well enough to even walk around with comfort is too much.
Left is the first best thing you can suggest. A qualified instructor is the second best thing you can get her. And reservations at a good restaurant will keep you both happy until she learns to shoot and you learn to cook.
