So I don't play a whole lot of Top, so I don't know match ups very well, but I can help with the other categories.
Items are very dependent on your champion. Anything that would help you kite is generally a good idea. For tanking, I could see getting an Adaptive helm with some armor items could go pretty well. In terms of actually slowing: Iceborn or Frozen Mallet for tanky/bruisers, Rylais for mages (the few that exist top right now), or Frost Queen's Claim if you're the support.
For playstyles, if you just wait out her cooldowns, primarily her ult or e, you can most likely win trades. You can also call out to your jungle if she's blown major cooldowns like her flash and ult and you can probably kill her and set her behind. If she falls behind, she can't do much.
For lane techniques, I'd suggest staying closer to the middle of the lane as to not be in danger of the wall tentacles. Also playing behind minions lets stay safe from her e which helps your trades a lot.
That's all I can really offer you, like I said, I don't play top much. I hope this helps at least a little bit![sg-ahri-2]