take her to the range, rent as many as you can... which one feels good in her hand and what calibur she can shoot, is the one you should get...Don't look at name brands, what maters is what gun fits, lots of women have probs reaching things like safetys or triggers on some guns Don't rule out a revoler A 357( you can shoot 38s which is important for a women) with a 4 or 6 inch barrel is a valid option.( infact it what I recomend)
Min for a auto is 9 mm, 32 H &R mag or 38 spl for a revoler.