It's this (though when I was struggling with chinups I first used a resistance band, as the level of assistance reduces as you get further up which more closely models the actual strength difficulty pattern of the movement, that first pull from dead hang to the 90 degree upper/lower arm at elbow is the hardest portion). She was obviously a little overweight so pullups were never going to happen, and probably wont at her current weight. Heavy male powerlifters have a similar problem as far as reps go).
8 - What the Heck Is That?! - The Assisted Pull-Up! - YouTube