"ADC that counter jinx"
http://i.imgur.com/d5PAtgw.png
http://champion.gg/champion/Jinx/ADC
so most of her hardest counters are champions where she just has a slightly above average winrate instead of a significant one. yup, this champion makes absolute sense.
edit.: i think what people dont realize is that she still has champions that she counters herself and has a far above 50% winrate against them. if she would sit at 50% against her "counters" and 50% against the champions she counters herself, it wouldnt be a problem. but as it is, shes either strong or very strong no matter who shes going into lane against. except for morde she has no actual counter, but still counters certain other adc.