"I hardly know her."
Translation:Téměř ji neznám.
This one is little tricky. We might need to select a different sentence as the "main" translation. It is the same in English, depending on which synonym for "hardly" you use.
I barely KNOW her.
I practically DO NOT KNOW her.
I virtually DO NOT KNOW her.
I hardly KNOW her.
Depending on the nuance of the adverb you might need to use either know or not know.
Já ji téměř znám - this would mean I nearly know her (as if you were to be introduced to her this afternoon so you are pretty close to knowing her).