While SA revolvers are not typially at the top of the list when it comes to self defense guns, in this case it may be worth considering. Two that come to mind are a Ruger Single Six .32 H&R Mag (some came with short grips even)--still a relative pussycat to shoot with Georgia Arms' nice 100 Gr JHPs, or the 3-1/2". Montado model of New Vaquero .357, shooting lighter/medium .38s -- or even the .45LC variant which would be lighter in overall weight, shooting midling .45 rounds. The advantage of either of these is that the hammer pull can be reasonably and safely lightened a bit without compromising the safe/functional operaration of the gun. My 4'10" 90 lb grandmother handled the old Colt SAA with aplomb back in the early 1900s Arizona frontier, so I'm sure this young lady could master smaller yet Rugers of the same basic--but even "safer"--design.
Not ideal, but the hammer pull, even stock, would be less of an issue, and operation more straightforward than an auto, and easier physically than a DA revolver. My vote for her: the slick, small frame and low kicking Ruger .32 SS in "Vaquerito" (fixed sight), 4-5/8" form. (Btw, Vaquerito not a Ruger term)