Alright, I am having trouble against Katarina.

She constantly spams her shureken and lowers my hp if I am playing a melee and trying to farm. Yes, my ranged teammate can *try* to stop her, but then she will start harrassing my partner and may eventually shunpo and gank on my partner.

Same things applies if I am playing ranged. I cannot win in a 1v1 if she shunpos to me. And will just throw the shureken at me if I try to farm. Then, she awaits a good opportunity to shunpo and start attacking me head on.

Help please.. This is probably the only champion I have major problems with.
Thank You

Its fair to say you won't know ahead of time if she's in your lane, but if you did, Doran's shield should be your buy.

Against Kat:
#Bouncing blades has a min # of bounces and is usually the first skill maxed. Simply put, let her rock your creep wave, and sit back and avoid it. It is worth losing gold by being pushed back to your tower rather than losing xp/gold for dying because you went up and killed creeps and kat killed you.
If she holds back on her BB and levels shunpo, even so, it shouldn't be enough to take you unawares without serious lanemate assistance.

Long story short: Assume she's going to win the push battle, and let yourself be driven to tower. You get less gold, but the same (/slash better) exp (/as we assume you don't die) and she's honestly not as strong lategame as people think.

Gaeb is right. Her late game potential is really lacking, hence why you see people try to make a name for themselves early then build her as a tank. Later in the game, because she may have snagged quite a few kills, people will try to focus fire her. Tank Kat with Shunpo to allies is very hard to kill.

Early on, just hang back and get your creep kills when you can. You will have a hard time winning the early battle, but if you are patient you'll win the drawn out war.

Try and setup a gank on her as early as possible (Keep in mind that she can shunpo her own mobs/lane partner to get away), because there's no way you're going to out-harass her if she's halfway competent.

As a Katarina player I can give a few things that I KNOW tick me off early game as far as melee people go.

Most melee characters have a ranged skill they can use that chips off a decent chunk of HP, those really can force Katarina back early game, she is a lovely harasser but you have to play the player, scare a katarina player early on with a death or near death and they will GENERALLY be much more timid. This doesn't mean charge into melee range through teams of enemy minions, get focused, and then watch as Kat laughingly finishes you off, this means do hit and runs with CC abilities and the like. Kat HATES slows, stuns, and silences as they neuter her early game from doing just about anything. You don't have to kill her, just make her worried that "one more of those attacks and some basic melee hits and I'm out!"

Time your strikes to creep waves, make her retreat when a wave is coming so she misses out on one or two minion deaths EXP wise, this can make a level gap appear faster than you might think, and getting your ultimate before your opponent can really turn the match. All of a sudden there's that one important enemy death that puts them behind and you in the lead for then, if kat is dead or back trying to regen/heal she cannot build up to a killshot.

Keeping her from the EXP and gold keeps her from gaining the crucial attack to HP ratio against your team and can render her meek endgame and easy prey. Nothing is as frustrating as being Katarina, never dying, but being utterly unable to kill an enemy Champion because you have a bad gap in levels and gear because playing conservatively kept you behind.

On the other side, too aggressive of a katarina will lead to a LOT of deaths and gold for your side.

I know that farming can be vital, but you have to time the farming to when you can force her back, get a feel for the timing of when she can and cannot bouncing blade, and if she shunpos don't be afraid to wail on her a bit with melee basic attacks, just don't chase too far. Early game especially one or two melee basic attacks does as much as a shunpo, and depending on the hero can do more than shunpo can.

TLR
Make her scared or make her die, hold back on the farming if the timing is bad...gold can come later, just try to keep her from getting too much either.