"Are you going with her to the park?"
Translation:Idziesz z nią do parku?
niej is genitive, dative locative nią is accusative and instrumental
(n-pronouns are used after prepositions)
You know, that's the usual "not-technically-wrong-but-doesn't-sound-great". Pronoun at the end of the sentence is something we really dislike, although sometimes it doesn't sound that bad. This sounds very much like "Are you going to the park WITH HER?", and this isn't even the word order of the English sentence.
So what about the sentence "Nigdy nie zapominam o tobie" (in this skill section)? Is it better to put the pronoun before the negative verb?