She is trying to isolate the copper wire with the plastic coating so that she doesn't get electrecuted by the exposed metal wire.
She is doing this because copper has a very high electrical conductivity. This means that it can easily transfer electrical energy to a medium (in an unfortunate case the medium is her)
so, she uses an insulating material that is the plastic (jnsulator). Insulators doesn't allow energy to flow through them so she is safe to touch it or even place it in a wet surface, as long as she isolates it well.
