Sometimes Hashem makes you a sheliach and gives you a tafkid to do. Once that job is over its over. You are no longer a necessary part of that person’s life and they need to move on. Please don’t be hurt by it. You did your part and fulfilled your mitzvah. Even though you would like to still be a part of her life and continue to help her, she needs to spread her wings and fly. If she fails, she fails. She will have to learn how to pick herself up, dust herself off and try again. It is up to HER to learn what her friends have taught her from being the best support anyone can have.
I am quite sure that she will never forget what all of you did for her. She may not be capable of turning around right now and showing Hakaros Hatov. Maybe in the future she will be, or maybe she will only be able to in her heart and never have the seichel or the nerve to do it face to face. Who knows? But know that all of you performed the mitzvos that you were supposed to perform. If you had it all to do all over again, would you do it any differently?