have bitochen and you’ll get over it!! you will inevitably leave the world when hashem destines for you to do so. never fear it, just prepare for it and don’t push things off!! always make sure you rectify your mistakes before going to sleep at night and you won’t go wrong..
As for fear of loosing another loved one chas ve shalom,everyone comes into this world to forfill a particular tafkid, you owe hakoras hatov to your parents for helping to bring you into this world to accomplish what you need to accomplish, however they to are human and will have thier tafkid complete after 120 hopefully and will return to our creator, the same will happen to you. that’s the way hashem has designed his creations. we are not here forever there is an eternal world that exsists outside of this one, which the nifteres has joined and become apart of. I think you should be happy for her that she was able to accomplish her tafkid and was invited to join everyone up there. You can continue to connect and be close with her soal, even though her guf isn’t here, by davening for her success and working on yourself in her zechus so that she is accepted in the highest position in gan Eden. Ask yourself this Question, will you want everyone to be depressed down here when you have accomplished your tafkid?? You are not giving her nachas by being upset about her leaving, replace the depression with accomplishing shas by her yarziet in her zechus, learning perek shira, etc.. working on personal growth in her merrit will help you as well as her.
May this Tzara pass quickly and easily and may you have many more simchos in replace. Amen!