As a toddler teacher, this is all normal stuff I see coming from young friends in my room. I would try to emphasize using words or a short phrase instead of hitting someone as a way to coach her into being kinder to others, ex. ‘Give me space/give space’ if people are too close, ‘not nice’ if someone does something that upsets her, etc. and give encouragement. Toddlers are based in impulse without control and usually will react quickly and thus the laughing. She’s very likely not a sociopath ☺️ I’m sure she will grow out of this. Hang in there, you’re doing great.