What does " her icy stare " mean?

It means the same thing as a cold stare. It is unfriendly and is generated by ill will or anger. (if someone is staring at you with a judgmental or angry face)

a cold dead lifeless stare or it could mean a cold heartless stare implying that she either does not have any care for what she is looking at as if she just doesnt feel emotion or that she is scolding someone with a stare but doing it in a way that just seems heartless.