That will be the "good end" then, she stays with Harry and Luca left but like others said she will never be the same again. Nonetheless this is the best it can be (exclude the Aya editions).
I've just played through all the endings, purposely left out all the ones with Aya at first. Then played all the endings that involving Aya, Aya Clumsy, Aya fallen, Good end Aya, now I understood what the others have been saying. AYA IS BASED.
Play through all those Aya edition endings, the more you play the more you see Laura is beyond saving even in those ending where Laura leaves Luca. In my opinion she was a slut before Harry, still a slut even ends up with Harry and always will be when she meets the "next Luca".
I wouldn't say that she's a slut specifically... rather, she's a nymphomaniac. A literal sex addict. At the start of the story, she's been repressing that part of herself because of the whole thing with her mother... but that just makes her weaker against Luca, while Harry was too unobservant to really notice this or push her on it.
At the end of the day, the fact is that if Laura DID accept that aspect of herself and she properly managed her urges with Harry... Luca would have never been able to do much to her. All he has is a huge dick, but he's not inherently superior as a lover, and if anything, he's actually incapable of really caring about someone else other than himself, which in the long run, would limit him. It's why the Good Ending works at all. Because Laura wasn't addicted to Luca, she's addicted to pleasure, and once Harry showed her that he can manage her full urges, Luca suddenly didn't have anything to offer her that Harry couldn't.
Basically, after the good ending, I very much doubt that Laura'd ever betray Harry ever again... because surpassing his ability to pleasure her would be impossible without a lot of work. He'd know absolutely every one of her buttons and how to push them, and anyone else trying to muscle in on the scene would have to start over from scratch.