i agree with the mossberg... maverick 88's are cheap enough and easy to use.
i also agree with the take her to a range with a flat of shells.
but one may argue with the order of that, when in fact that may be back wards!!! ya might want to take her to the range first and let her shoot before the purchase of a gun she wont be comfortable with. the big thing to remember is to not stop there if you really want her to be protected and feel secure long term you should take her to the range more than just to fit her with a gun...have her use to using it and have it in her mind that it is a go to protection weapon.
either way good luck.