Complex sentence: Although she seemed to know what emotions she was supposed to show she was often out of sync with the feelings of everyone around her, and even people who knew her often found it very difficult to discern her mood.
Split into simpler sentences: Although she seemed to know what emotions she was supposed to be feeling, she did not exhibit them in a normal fashion. She was often out of sync with the feelings of everyone around her, and even people who knew her often found it very difficult to discern her mood.