What does it mean to add thank you after the text message?

According to the information you provided, it is difficult to determine the specific meaning of the girl. However, we can interpret her short messages from the following aspects:

1. Thanks for dinner: This may just be a short message from a girl to express her courtesy and gratitude, which doesn't make much sense.

2. Implied refusal: If a girl is not interested in your date, then this text message may be her way of expressing gratitude and implying refusal.

3. Hope to keep in touch: If the girl is satisfied with your date, then this text message may be a signal that she wants to keep in touch, not a signal that she refuses to continue dating.

Therefore, I suggest you wait for the girl's reaction to see if she is willing to continue dating. If she likes it, you can learn more about her thoughts and feelings in future dates. If you don't want to, you should respect her decision and continue to look for the right person.