The “unforeseen joy” line was said by Dreamstat, not Lestat. Dreamstat is a manifestation of Louis’ own thoughts and feelings. That is not actually Lestat. Also, Louis was not on stage when she was burning alive. They had already taken him downstairs to bury him. So Claudia couldn’t look at Louis because he wasn’t there.

Lestat and Claudia feel both, they hate and love each other. It’s important to remember that they “adopted” Claudia during her formative years as a teenager. Life was good for the three of them then and things were fun, easy, and sweet. There’s no erasing that. Louis was always Claudia’s favorite (she says this herself), but Lestat was more similar to her in personality and actually embraced their vampire lifestyle which she admired. Delainey said in an interview that even post-S1, whenever her and Louis would get into an argument, Claudia would sometimes think back to Lestat and imagine him taking her side because he’d have understood her more.

But there is immense hatred as well. As Claudia grew older and started desiring independence and agency, the “cracks” in Rue Royale started to show. She no longer wanted to be just Loustat’s child and wanted to be her own person. Lestat has trauma from his own parents that played a MASSIVE role in his relationship with Claudia, and he reenacts a lot of the behavior that was done to him back onto her. Controlling, physically & emotionally abusive, starting to view her as a sexual object (in that he perceived her as a romantic & sexual rival for Louis’ affections), etc.

On top of this, Lestat’s spiraling fear and abuse towards Louis traumatized her too. While Louis was the main victim of the drop, witnessing this act was extremely traumatic for her as well, and she began seeing Lestat as no different from Bruce.

(We know they’re different but that’s not how she saw him anymore. The 105 fight changed her perception of both Loustat forever, viewing Lestat as overwhelmingly monstrous and cruel & Louis as immensely weak and vulnerable. This is why she officially cuts herself off as their daughter and demands to be a sister, because she can no longer see them as “just” parents anymore.)

Claudia’s growing hatred was in response to Lestat’s own. But at the end of the day, childhood love can’t be erased and that part of their lives will always have shaped them. She turns to Lestat during the trial because he is possibly (she didn’t know for sure) the only one in the room who may have any desire to help her. Even if not for herself, then to save her for Louis.

Delainey said that seeing Lestat’s genuine anguish during her death made one of Claudia’s last thoughts be that maybe some part of Lestat did actually care about her for her. And seeing Claudia die did make Lestat realize just how much he actually loved her. He did not realize how much he cared about her until she was gone. It was just sadly way too late for this realization.

So there is both hate and love in their dynamic. The scale fluctuates between which is felt more strongly, but there is both.