weak pre-5 can run into energy problems so keep an eye on her energy she can actually get low and give you an opportunity to attack her escape mechanism is nullified by a pink ward. Get a gank and pink ward her shroud and she'll be very vulnerable (be aware of where the minion waves on the way to lane are so you'll know if she can dash to them to escape) health and mres will obviously help. Get a hexdrinker and then a big health item. She likes wars of attrition and if you can beat her at that she will be worse for it. During all-ins, ignite her very early, her spellvamp adds a lot to her in terms of tankyness and makes her harder to kill than she appears. AoE abilities like Garen's Judgment do well to damage her in her shroud. Reveals like Lee Sin's Tempest or Sonic Wave are great at messing up her shroud just like pink wards are.
She's the stickiest assassin in the game, with one of the largest amounts of magic instaburst, surpassed only by LeBonk for single-target ownage. Gank her early to give your teammate an edge, and late game have a tank initiate with an Oracle so you can nuke her while she's in smoke mode.