'ciebie' is the emphatic version of the pronoun. Using it in the second part would make it sound like changing the subject. "I hear YOU, Lauren, but I do not see YOU, Steve."
"I hear you but I do not see you." is the main answer, so your version with "don't" should work automatically. Must've been a bug.
Is "nie widzę cię" just changing the importance of you to see or is it just grammaticaly wrong?
"Nie widzę cię" is a perfect sentence on its own, because if you use only those three words, you don't have a better place for "cię".
But in this longer sentence, you can avoid putting "cię" at the end, so you should do it. "... ale cię nie widzę".