How to play\what to pick against Janna?

Hello there. Serious question here.

I am a Janna main (not long time but still) and I am desperate at finding counters to my own favorite\personal freelo champion. In fact, Janna carried me more than 1 tier already. Any lane I'm facing seems at least bearable and most of the time just stupidly easy. Any support I face can't do anything significant to me and my adc. I can even counter 3-4 man ganks most of the time. Late game depends on a relative skill but when I cancel an entire engage from the enemy team it feels like cheating. I am on a verge of starting to call her op. Yes, I know she gets nerfed a bit on the PBE, but her main strength remain relatively untouched.

So, the question is in title - how do you counter her? My second support champ is Leona but it generally doesn't work due to being a natural counter.

Edit: Nami is probably a good choice. I am yet to lose to a Sona (can shield most of her Q poke and stay behind to not be double Q'd with my adc) and I've found a working strategy vs Blitz, so he no longer counters me as well. I've faced one Nami recently and just could react to all her poke with a shield (not anticipating but an actual reaction). Probably she was just not good (I am in gold anyway)