Do you think they had chemistry? Because I didn't quite buy it. Their kissing scene (after her hair is cut) is painful for me to watch. I liked how Jason was...protective of her, telling her to look away from crime scenes, and 'Don't look!' during the car chase...but...I just didn't buy the attraction to each other.
I think I can help here... that is, if you are prompting discussion and not just sounding off with your opinion.
Jason is being reluctant, and I think you interpret Damon's excellent acting here as lack of chemistry. Look at the facts first and only then think about any possible romantic attraction.
Jason paid Marie $20-thousand to drive him from Zurich to Paris. That's 400 miles and takes less than a day. She has to assume that he's in incredible trouble and that's he's very wealthy. Add the fact that she's seen him disable Castel in an extremely violent fight that left her in shock, nearly catatonic. In her eyes, Jason is nearly a superman. She's in the presence of a man who can protect her and provide for her in a way no man she's ever seen can protect her and provide for her.
Marie's a fairly plain young woman. She knows that she's not a great beauty. Nevertheless, she's in the presence of a strong, confident, exciting young man-of-action who apparently is also very rich. She senses danger, so she's reluctant -- recall her reluctance in the car before going with him to the front door of his apartment building -- but she's also extremely excited (in a subdued way) by Jason and strongly attracted to him because of his manliness and wealth (and his terrific attitude). What woman wouldn't be strongly attracted to Jason? He's emotional dynamite with an extremely long fuse.
When she comes on to him, he's reluctant at first. Of course he's reluctant. He's aware (from his perspective) of everything I wrote about above (from her perspective). Nonetheless, he's horny, and while no great beauty, she's trim and slightly attractive, so he gives in to her advances.
Now, watch that scene again and see if your opinion about lack of chemistry survives.
Ciao _____ I don't have a dog. And furthermore, my dog doesn't bite. And furthermore, you provoked him.