No matter when, sister is sister, she will love you very much. As for thanking, it is totally unnecessary. Just accept this love and care, and then let her worry less about you. As for gifts, I can give you some small suggestions:
First, send a simple blessing to sister. Since she is still a student, don't send too expensive gifts. Send a greeting card and write your blessings.
Second, send a gift she likes. You can send a similar bag or perfume. I believe that a sister who loves beauty will definitely like such a New Year's Day gift.
Third, send a creative gift. A crystal music box is good. The charming purple color and nostalgic music will make sister return to her childhood. You can also give her a big teddy bear, a cute gift, and girls will like it very much.