Looks like someone has finally caught on that she is ahead of the pack. I picked her up about two weeks ago when I was Silver 4, and did really well with her. I climbed to Silver 1 with her (had like a 100% win ratio for like my first 12 games with her) specifically by rushing a mejai's and stacking it up with my ult. However, it has recently become harder for me to do well with her primarily because her only escape and hard lockdown is her Q, and man, people actually know how to dodge abilities as you climb. Just choose assassin champs with good gap closers (Warwick, Talon, Akali, Katarina) and that will help shut her down hard.
Late game, focus her hard in team fights, as her ult does massive damage and has a very low cooldown.
TL;DR if you are having trouble against her, just make sure you dodge her Q, as her combo is devastating if she lands it.