Pantheon goes well against her. Teemo if you play right. Lulu destroys her so hard it isn't funny.
I like to go Galio as you are always out ranging her and hardly need to use your melee to last hit. If you do you can force her away easy if you shield your self and just trade with her.
Anything with range tends to work, as long as you watch for the E's from her you should be good, early game getting hit by a Q doesn't give her back as much Health as she would want, and costs her more mana as @Nep2une said. So you can just force her to waste mana by dodging her moves.
Split pushing is another good way to wreck her day. If your team is coordinated you can ask them to push one lane as 4 and you just stay top and push it so hard she can't leave.
is good at 1v1 sure, but she really does best in team fights, so she wants to join her team as soon as possible. If you force her to stay in lane your team has a higher chance of winning the 4v4 trades compared to 5v5 with you and her there. Push so hard it makes 2 people come to you and then your team can win the other lane fight or push them self.
Most Illoai players will give up pretty quick when stuck in lane and will roam or try other things as they just get bored dealing with you over and over.
ALSO GET A FUCKING MORTAL REMINDER. Seriously people. This item destroys heal based champions, and she is one of them, she relies heavily on her tentacles landing on champions for health back, if you just half that amount she will die in more than 90% of her trades against team and solo.
These items. Or Morello if you are a mage. This will shut her down early in any trade, so use it for crying out loud.