I'm currently in my first week on saturday and in a cafe with Bituka about to take pictures.

While chatting she apologizes for a pub night and something about me being drunk.

But I never went out with her, just met her at the gas station and agreed to help with her father.

Did I miss something or is this a dialogue error?

I would need to check your save to know which choices you missed having that dialogue. Also, please keep the game updated to the latest version if possible.