Li Fan wasn't unable to control his hand and grope Li Wugou unintentionally. He did it on purpose... er, that's not quite right either. In fact, he was covertly testing Li Wugou's cultivation level.
This was because Li Wugou's situation was truly odd, neither good nor bad. You could say that her ability to fly, resist knives and spears, and extend her fingers to gouge out eyeballs and peel foreheads made her seem like she was using some evil sect's demonic technique—not at all like the orthodox practices of Xuanmen.
