The best picks out of lane to counter Senna include Kalista, Lucian, and Zeri. These champions are all great at countering Senna with high win rates over 57%. Even if these Senna counter picks are not picked in your lane, it's not a good idea to choose her into any of these matchups. They will usually beat Senna.
Yet, if the enemy team choses either Karthus or Swain, you should seriously think about taking her, as she easily destroys these champs with win rates over 53% against both ofthem.