Haven't seen the loop type. Decades ago, when optical sights became popular on 1911s, perpendicular metal charging handles were brought out to enhance slide operation. However, these were geared for bulls-eye guns that lived in gun boxes, or IPSC competition holsters that stood out from the body, and were never really adaptable for concealment.
A high, sturdy rear sight with a square edge that can catch on a sturdy belt or holster works well for one-handed charging though the shooter must take particular care to keep the muzzle pointed in a safe direction. Some of CZ's pistols have sights high enough that the support hand can use them as charging handles if need be.
With an auto that has an external hammer, earing the hammer back before racking the slide relieves mainspring pressure and reduces the tension the operating hand has to work against. Most striker fired pistols have easier-operating slides as a general rule.
A 1911 with short (standard) recoil spring guide rod can be cycled by placing the front bottom edge of the slide against the corner of a table or counter and pushing the frame downward. Care must be taken to keep the muzzle in a safe direction and, of course, fingers off the trigger.
And of course, there's always the revolver.
What sort of pistol does she prefer to use?