I'd suggest that we avoid telling any scary stories with Janet around. She’s a bit unstable and could get hysterical.   

A It is no fun to tell frightening stories to Janet, who is not very stable mentally, because she only laughs instead of getting scared.  

B Janet has trouble keeping her emotions under control, especially when she is told frightening stories.   

C    Since Janet is somewhat unbalanced, the only way to make her laugh is by telling  stories, but we should avoid scary ones as they might cause her to panic.    

D Janet is somewhat mentally unbalanced and might easily become uncontrollably emotional, so let’s not tell frightening stories in her presence.