I just played a bots game to try her out, and don't know if this is intentional or not, but Senna's Q can target and damage structures. Turrets can be targeted by some abilities, I realize, but what makes me think even more that it's a bug is the fact that it can target and damage both inhibitors and the nexus, which, to my knowledge, no spell in the game can directly target or damage, aside from auto-attack buffs like Viktor Q or Twisted Fate W, though TF W only gets consumed on turrets and Viktor Q doesn't get consumed at all. The tooltip for the ability does not say it can damage structures specifically either, only enemies.
Steps to Re-create:
1. Walk up to a vulnerable structure as Senna
2. Press Q on it
This is infinitely and easily repeatable, and is fairly self-explanatory, thus I see no need for a picture or video. While I can see that it might work as an auto-reset, I am unsure if it is meant to be used as such because that is not its only effect.