Personality-wise, Tatsuki is protective and level headed most times, unless someone has done something to her. She uses her great strength to beat up anyone that bugs her. Strangely, she has a lot of insight on Ichigo's personality.
Tatsuki is best friends with Orihime Inoue and is constantly protecting her from men looking for a date, as well as Chizuru Honshō, the school lesbian, who often approaches and grabs Orihime's breasts. Tatsuki has done this since middle school, when she beat up some bullies that were trying to cut Orihime's hair, and had already done so once before her brother died. After that, Tatsuki promised to protect her from anyone who dared to make her cry, and she and Orihime became best friends.
Like many of Ichigo's friends, Tatsuki is spiritually aware to the point that she can clearly see ghosts, hollows, shinigami, and other such supernatural phenomena, though she lacks any unique spiritual powers of her own. She is strong enough to survive spiritual attacks most humans are incapable of dealing with, though this may be due to her karate training. She also has the ability to sense Orihime from almost anywhere, even across dimensions; she is able to sense Orihime when she travels to Soul Society, but remarks that she can't sense her presence after Orihime is taken to Hueco Mundo.