Actually, it's just a thank you, not a promise. The paper is sealed, and no one can find it except the special channels of our school. Girls' minds are always delicate, and the master's thesis is a farewell to this period. Girls usually want to leave a souvenir and a paw print. Thank you can be understood as someone who is helpful to the paper, but your girlfriend has always supported you mentally. I don't know if you ever complained to your girlfriend when you were worried about writing a paper. Anyway, I comforted my boyfriend when he was worried about the experiment, reminded him of the paper all the time when he was busy, and tracked his progress.