Tbh, the fact that Clarke is happy and has a ligher vibe to herself after 6 years makes me so happy. We don’t know what has happened in the last 6 years, but she finally had a break from hard decisions that ripped her humanity and just had to focus in survive (and she even found company) and look at the sky to the day some freckled guy fell from the sky.
They are both miserable without each other and it's so sad. It's also what speaks most for them being together in the end. I think he kissed Noora to get over Sana but it didn't work and in the process he screwed things up between them. But I think that as long as he's honest to Sana and don't lie about or come up with stupid excuses, I think they can make it. She's not over him, he's not over her. They must be together!