Complex sentence: She is certain that he is behind the recent thefts, as she realizes who Robie is despite his use of an alias, but at the same time she is attracted to him, even offering to help him in the supposed thefts.
Split into simpler sentences: She is certain that he is behind the recent thefts, as she realizes who Robie is despite his use of an alias. But at the same time she is attracted to him, even offering to help him in the supposed thefts.