If she calls, give her a few minutes to tell you why she is calling. If she doesn’t get around to it, tell her that you are very busy, wish her a good year and a good life. Say it like you mean it, but make sure you don’t say it like “talk to you later”. Then hang up. If she calls back let her know that you have moved on from High School. Let her know that you don’t have enough time to keep up with family and friends you have as it is and although you have nothing against her, and you are not trying to hurt her feelings, you just not possible for you to give another friendship the time and energy it deserves. So although it was great hearing from her and you wish her all the best, you don’t have the time and energy right now for catching up.
Do you think you can do that?