How do I deal with Akali?

So I've been at this game for a shorter period of time, learned how to deal with things. Except one damn champion. The burst-DPS, hypermobile and if they get a Banshee's, untouchable Akali. I've failed to see how exactly one is supposed to deal with an Akali who has only 2-3 kills - but is still able to delete your HP in a matter of seconds. Usually what happens is that she hits a flash, uses her ultimate to hit me and can then burst me, regardless of whether I try to escape or not because the same ultimate can be RE-USED. I'm just baffled at how a champion seems that damnable powerful, yet people aren't talking about her. That means there's a certain aspect I do not know of, which I'd like to ask about today. Thanks for reading this over.