Have taken a deer with a 50 cal round ball,60 grains 3f,about 70 yards.(1-66"twist.) Took out rib and vertebrae. Trying to work up a light load for a friends inline we had poor bullet performance (recovered from backstop),he used roundball that year but large bullets would have left a wound channel sufficient?given proper placement. Not to crazy about roundball in a fast twist.
Maybe sabots for smallest effective caliber with squab load of powder for her?
Frm an enclosed blind a leadsled or similar on a table or turret would help on recoil,positioning it by herself could be a challenge.