So as the title says how the fuck do I fight 
as a melee champ cos every time I go into this match up it just feels like I don't even have a chance to fight her and if I ever go in on her she just destroys me
You don't ever go in unless you've pulled her away from her tentacles. Her tentacles are stationary and take a fair amount of time to respond. If you don't ever get into her range, you'll force her to approach you, which severely limits her power if you drag her away from her tentacles.
If you don't wanna play a ranged champ against her, a lot of melee champs can work. They are just really fecking hard - You have to dodge EVERY. SINGLE. TENTACLE. A lot of her damage comes from slapping people with her tentacles. Thus, dodge all the tentacles, and you should be mostly fine. Also, kill the tentacles. ALL the tentacles.
Ranged champs mostly have the advantage because it is easier to dodge tentacles when you are far away from her.
Someone with mobility (like riven), should be able to dodge easily.
I've found that not standing still helps. As Nasus if you can walk circles around her and keep your autoattack rate high, you just kinda win when all of the tentacles miss.
If you want to beat Illaoi as a melee, you want something that can out sustain her.
As someone who actually plays this monster (ducks the flying downvotes), I find that Nasus it pretty much instant GG against me. He pops his ult... I pop mine... and though it looks like I'm winning the trade at first, I inevitably lose. He just has too much lifesteal for her.
She says how you fight her, "move!"
bait out her test of spirit mostly.
take out tentacles while shes out of lane and when shes going in for cs.
i think the most important thing to remember right now is that you dont actually have to beat her in lane. you just have to stall to mid and latgame and not die. she falls off like a rock.
Teemo is extremely fun against her :P
Ideally you don't play melee Champs into Illaoi--she has the potential to kill just about any champ who lingers around in her Sphere Of Influence and is gated only by skill. Ranged toplaners with %hp damage--like Gnar or Quinn+
+%arpen item--are probably the best way to deal with her.
If you do get caught in a bad matchup, rush a lifesteal item so you can heal off the waves. Stacking HP isn't as important against champions like her. More movespeed helps, as well.
Have you tried crapping on her chest yet? I've never had a problem destroying her as Mordekaiser.
Don't fight in her ult for starters.
Trynd, Yasuo, and Pantheon do well against her.
dodge the tentacles and she's not that tanky or if you can fight tanky champs don't dodge them and just deal more damage
remember that she has to stop hitting you to hit you with tentacles unless she's using W with a nearby spawned tentacle
you don't fight her really. the best you can hope for most of the time is to go even unless you are another high dmg juggernaut or carry who can dodge her abilities.
she does have her same shitty kit as ever even if it is severely over tuned right now. her Q is slow, her tentacles are slow, the E is dodgeable.
where illaoi really is a nuisance is her ultimate. it is basically a "you have to disengage button." if she ults you run. thats the only counterplay unless you are WAY ahead. if you are super far ahead sure, fight her in her ult and just burn her down. but if you are only slightly ahead she will kill you. hell she will 2 v 1 in that thing.
its a piss poor design on the ult and the E. the E is dodgeable but super annoying to deal with unlike any other debuff. and the ult is just a free "get away from me button". she can slam her ult you have to back off and she runs away.
she has her weaknesses though, unless someone is locked down the best she is gonna do in a team fight is zone really hard. as most people have learned by now to just run away from her.
i think as a melee champ you have to be quite skilled and rely on your ability to not only bait her but dodge her abilities as well as only trade when her E is down. if you try to trade when its up she pulls your spirit and you lose the trade.
its a nightmare to deal with.
she's beatable, but way overbuffed to make up for her awful kit design.
Good riven will destroy Illaoi Just e her e and kill her. As Fiora q her e and ult her then dance around her. As poppy,Trundle,darius dont try to fight her after first item (any item) instead do early kill and she will be behind, BUT DONT GET COCKY THAT KILL STILL MEANS NOTHING IF SHE GETS ITEMs.
Its a bait game. You get her to use her ult then run. Then run back in. Dodge her soul grab and its all good. Easier said then done though.
depends on the champion. On most champs, you're fucked, but on some more mobile once that can avoid her tentacles and E, you can actually all in and outplay her pre 6. She isn't that tanky early on, especially if you avoid the tentacles and thus deny her heal, and without her tentacles you have agood chance at aouttradeing her. Though it's always a skill matchup. For the fucked champs, just focus on surviving and look for opportunities to impact the map with roams/tp. Illaoi scales bad into lategame usually, as it's easy to disengage her ult, and after that she's rather usless in teamfights.
