Yes, that scene with Lumen stepping in front of the video was intense, as well as the kill and the moment when Dex gave her the tape and he listened in as she watched in the next room.
The scene where she came out dressed in her "kill outfit" and Dex gave her the gloves made me smile. I know, it's weird! This could only work with a character like Dexter. Two serial killers bonding-awwwwww!
I wish Quinn didn't have to go, but if he makes it past this season next season will likely be his last. I think he just knows far too much to ever just set it aside. Perhaps he will think that Dex fell under Lumen's spell and is helping her clean up her messes but is not actually a killer himself.
I hope Lumen gets to run off and live her life. I have a feeling that if she does we will see her again in the future of this series. Perhaps Dexter not showing her the entire code will come back to haunt him as Lumen won't be able to stop seeking justice for other victims but without Dex's resources she may end up killing an innocent or two. Then Dex will be left to track someone he trained and had feelings for. He may recognize her handy work at a future crime scene and then must hunt the person that he taught. We've seen glimpses of that in the past but not with a character that is not truly twisted or evil, just a lot like Dexter without the guidance. Would be nice to have her live and see how this thing evolves for her and the consequences that Dexter must face for teaching her his craft.