Marisa's faults are very much well-known in the Touhou fandom: She blatantly lies without effort; Her two signature spell cards, Master Spark and Stardust Reverie, border on cheating; She constantly steals books from the Voile Library and also stole the Master Spark from Yuuka; She's prone in getting into fights easily; Her house is an awfully massive mess; She compulsively hoards stuff; Her curiosity usually gets the better of her; And, most of all, she is seen as a obnoxious imposition to others, even by the people closest to her.
But see, this is because Marisa usually does what she wants, and I've always loved that sense of freedom, liberty, and independence from her. Her faults also charm the fanbase mostly, and ZUN said that Marisa is the closest relatable character to humanity so far. Also, this personality of hers, the faults and all, is what attracts me to Marisa, if were talking about internal traits.