She isn't that OP, she's strong but not near that. The main problem is that people run away instead of trading when she E's, which makes it impossible for her to debut you.
That being said I'll give you some nice tips for her. Firstly, pretty obviously is to fight in your tentacles. When you E, and they try to fight you, position yourself to hit the spirit and the champ, you get anywhere from 25-70% EXTRA damage.
She is a lane bully aswell, but a weak duelist. Just harass if you are against a dueling champ. Also it is really tempting to wave clear with her abilities, but learn to not wave clear too often, as you need poke to make up for weak all ins (besides them standing in your tentacles like tards)
Don't push with abilities, only freeze, early you are super easy to gang
Also, when the jungler ganks you is when you are strongest. You go from being a weak duelist to a god 1v2. Even whIle two kills behind, you can manage to 1v2 if you play correctly. If you are a kill behind you only need about 1 tentacle then a two man ult. Just keep W-ing and healing and position well, you will almost always come out alive, with a double (unless the enemy is one of her counters)