Hand gun is better than a long gun for cross eye dominancy, there are 2 ways commonly used, cant the pistol toward the dominant eye, just about 15 - 20 degrees, or more until the dominant eye takes over, or bury the head into the strong arm bicep, so the weak eye is below the line of sight, but the strong eye is level with the sights. The 3rd way is harder, and that is to teach her to shoot with the weak arm and dominant eye.
For personal protection at 20 -30' it won't matter much, but let her try these methods and see what she thinks. The weaver hold works really well with the buried head technique, the pistol cant works with the isosceles hold better.
I hope this helps.