How to deal with anivia

Recently a lot of people I encounter play I just have a very hard time to win a match and I have always lost a match against an . I play top lane and I try to at least get fed which I will win my lane 85% of the time and even if i get fed she can just whoop my ass. Every time i see her she is just fed will always beat me and has stop me from climbing the ladder for 6 months. I keep thinking I can win this so I switched to mid and my god its impossible. I can dodge her q and e but once she reaches level 6 I cant beat her she just spams her ult and then use the e to kill me instantly!. And on top of that the rest of the team will be so tanky. For example I always see They will keep her alive constantly and its very hard to kill her I need some help please let me know its impossible for me to win and I am tired of losing against this unfair balanced champ.