Punish her for farming, she has to get up close to farm.
When she's got a few levels, her sheen and some AS she wants extended trades and fights where her Hiten Style will build up a massive advantage over time in self-heal and true damage. Burst her down before she can manage that.
She's not innately tanky, not more so than any other bruiser anyway, the only tank stat she gets from her kit is her tenacity, which is only 10% in a 1v1.
And if you're having trouble with her, for goodness' sake play her next time she's free, doesn't matter if it's vs bots or whatever, but play her, learn when you feel weak and when you feel strong, what you have to get to do and what can shut you down.
P.S.
Oh, and Randuin's/Frozen Heart hurts her DPS really badly, especially if she doesn't have more than one or two AS items.