I don't think Eteri is evil :dev3: but she does prefer winners and simply spends more time on them. Although Kostornaya is new and Polina has been sort of on the periphery due to her illness (and were they ever close?). So that may be the reason. If it's not just accidental as I have said. Other Russian coaches seem to refer to their students by their first names, that's why it made me wonder.
Knowing Eteri I don't think it's accidental.
I recall that I read some time ago that when she wasn't happy with a boy's skating she used to call him using the feminine version of his name.