cut sb dead

cut sb dead
(to pretend not to see or recognize someone that you know, or to refuse to talk to them) — игнорировать, не замечать; демонстстративно не замечать; демонстративно не обращать внимания

Example 1: I said "Good morning" but she just cut me dead.

Example 2: How can she be so cruel as to just cut me dead like that? I feel so hurt and used.

If you cut someone dead, it does not mean that you kill them. It means that you deliberately ignore them and don't speak to them in order to show you are angry.