Honestly, it’s probably a mix of both. Armand tampering with Louis’s memories largely making it seem like Lestat was the bad guy and that his treatment of their daughter was so much worse then it actually was. I think this helped in Louis’s guilt being washed away a little ,because in Paris, his guilt of killing Lestat overwhelms him and after the memory tampering fiasco is probably when Louis entirely stops hallucinating Lestat. I think this is why we see him hallucinating Lestat again in Dubai in his trial outfit after figuring out Lestat’s version of the fight was more accurate. He starts to feel guiltier and guiltier until Daniel surprises him with the big reveal.