What I would do is make a Node2D that is a child of the player. Put a sprite into the node, and offset it to the right. Then, in a script, in the _process
function, I would write:
look_at(get_global_mouse_position())
This needs to be in the Node2D, not the sprite. Also, make sure your sprite is facing to the right, or else it won't work. You could also do this:
look_at(get_global_mouse_position())
rotation_degrees += offset # Offset is whatever your offset angle is