Vika has had a long standing coach named Sam Sumyk. Most of what I know about him comes from this brief interview with will Hamilton of Fuzzy Yellow Balls. What is clear is that their partnership works and there is no indication of it ending any time soon since Vikas amazing success has come with Sam at the helm.
Like Patrick mouratoglou for Serena Williams, Sumyk seems to have a very calming effect on Victoria. Vikas game is like Novaks. No major shot but highly consistent and she never gives up. Her biggest strength, her mind and unrelenting will to win, is also her biggest weakness. Her problem is choking, like she did in the US open final of 2012. So of course that seems mainly to be what Sam works on.
Sam knows see she has all it takes to be a great player and Vika trusts Sams judgement. Maturation and experience are what is required. They could copy the men and bring in a named player as coaching support. A Navratilova or Billie Jean King but I’m no sure that the women can afford these luxuries or whether it would help. It’s such a personal choice.