She should not have said this because the desire to quit smoking needs to come from her own deep motivation. She only succeeded in motivating you.... because you care about her so much. I'd just keep letting her know how important she is to you, try not to be too disappointed ok. She will get there.
Tell her your gonna fail if she dont stop smoking lol she will really hop on it and stop smoking or say today at school we learn about the harm and the badness of smoking or you could say mom im working on a project where i need you to stop smoking for a while and maybe she will get use to not smoking and stop
Congrats on your good grades! At least you got something really good out of it. Thank her for the motivation and remind her of the deal you had made. Quitting smoking is hard and she might be trying without you knowing. Anyway keep up the good work!