“this is her” makes more sense to me.

lets look at the conversation as if we are in a room.

lets assign person 1 as the one asking and person 2 as the one answering.

person 1: “can i speak to anna?” (in case P1 doesnt know anna) or if P1 knows anna then P1 points to anna and say “can i speak to her?” P1 and not “can i speak to she?”

person 2 answers back: (in case P1 doesnt know anna) points to anna and say “that is her” and not “that is she” or in case anna is right next to P2 then P2 say “this is anna” or “this is her” and not “this is she”.

now if P2 is anna then it makes sense to me and its sounds right to hear it as “this is her”

please enlighten me. thanks