How to fight ahri???

First thing to mention is that Ahri has 2 playstyles she can adopt, the first is the one you're probably concerned about which is assassin Ahri, in order for her to utilize this playstyle however she needs to snowball, if she goes even or falls behind she will need to fall back on her role as a kite mage as she will lack the burst to one shot most enemies, playing safe and not dying to Ahri while keeping up in levels and farm will prevent her from snowballing off of you. Ahri does have very effective roams, so you also need to watch for her to disappear from lane, signal your allies so that they know she is missing, do not blindly follow her as she could be waiting in a brush to ambush you when you attempt to follow, try to keep vision up as much as possible to keep her from surprising your side lanes. Ahri is also very mana hungry early on, anyone that can easily push the lanes will force her to use most of her resources for wave clear and not on you. Ahri also struggles vs health stacking, and resistance stacking to some extent, a Cho'Gath or a Diana that rushes abyssal will be pretty safe from being one shotted by Ahri unless she gets a fairly huge lead or pokes them down first. She is also extremely squishy, CC and burst can cause her some serious trouble, Malzahar and Leblanc are some of the best examples of this, Annie has a good mix of both of these qualities.

CC

She struggles to clear early and can't farm under turret well (both her W and Q have abysmal base values at low levels), so shoving aggressively can work out well, although she also gets nasty in gank assists. If she ults in early, you can gank her when you get back to lane, since she won't have a solid escape.

Laning against her preferably play a long range poke champion or a sustain champion (lux and chogath both come to mind.)

If you get counter picked by an ahri stay behind your minions so that she cant charm you. She may try to poke with her Q but as long as you dont usually get hit both times you should be ok.

Counters to ahri: Malzahar, Diana, Annie.

Counterplay to ahri: Early ganks, hard cc, burst damage, not staying in lane at low hp

Ahri is a squishy kite mage. She is no longer an assassin and can't 100-0 anyone if not fed. She can't kill you in lane if you don't let her poke you to under half health then let her all in you.

If you're playing against Ahri, dodge the Q poke. The best case scenario for an ahri is to hit both Qs on you while simultaneously hitting most of the minion wave with it - so don't stand near the minions. Make her choose to harass or waveclear. If she chooses to harass then do your best to dodge and push in the wave, she'll fall behind pretty quickly. If she chooses to waveclear she hasn't poked you down and she has no kill pressure on you at all - if you're uncomfortable just take the farm lane and ask for ganks (or roam yourself).

Ahri has some built in sustain so slowly poking her is senseless. Either damage her a lot and follow up once you get your cooldowns back, or don't bother and just try to outfarm her and pressure the turret and other lanes.

Then obviously, dodge charm. Dodge R--E combos. Once she gets to 6 you can start standing closer to minions since she won't have the mana problems as much anymore, so use the minions to block charm. If she misses the kill when she goes R-E make sure to call for a gank within the next minute as she should be an easy kill.

WHY? its doesn't matter

#AHRI IS SH*T

you wont face her