Actually, it isn't too surprising.
You have watched Pellington for the past 2 years. She is totally undisciplined. Even the way she drives in and just throws the ball up - usually not even looking at the rim - evidences the lack of focus and discipline.
She drives with no real plan, loses control as often as not, and often loses all control. Her quickness at times allows her to recover - but she is just totally undisciplined.
That is one of the reasons she is so weak at free throw shooting - and has been a horrible shooter at even mid range. I doubt she ever seriously has - or does - practice to improve her shooting skills. Watch her shoot free throws. She doesn't actually shoot them. She just throws the ball in the direction of the rim.