Following her sister’s death, Dani speaks to her as if she were still alive, and she gets upset if anyone tries to reason with her. What is the condition described here?

depression
denial
post-traumatic stress disorder
anxiety

Denial

Explanation:

This is a clear sign of denial.

Denial is a defense mechanism which is when someone refuses to accept reality, blocking out events from their awareness. If a situation is just too much to handle, the person may respond/react by refusing to believe it or by denying that it exists.