I think you are right. Your sister is bored with her life and maybe jealous of yours. Instead of finding the energy to get her own life on track, it’s easier to pull you down into her rut. Being a good person, you try to help by giving her attention and time. Sadly, it just isn’t helping. In fact, it’s enabling her to stay in that rut. As long as she is talking and talking and talking to you, she isn’t getting off the phone and into life.
I hope you will find a way to feel okay about putting an end to this routine. It’s not helping either of you. In the most loving way possible, tell her that this is your time to do your studies and to explore life at university. Tell her that you are happy to talk to her once a week to catch up and maybe to check in on facebook or by email every now and then. Stress that you have confidence in her ability to find friends and to get on with her life. Suggest to her that what she needs is a professional counselor, not an amateur like yourself. Then stick to it. Set up a predictable time to talk to her for an hour each week (like, say Wednesday evening from 6 – 7) and don’t answer her calls at any other time. Send her a quick message of caring now and then on email or FB but don’t get into an additional conversations.
She will be mad. She may say terrible things to you. Please don’t take it personally. She is scared of dealing with whatever is holding her back. When you draw a boundary, she will have to look at whatever is so painful to her. It will seem easier to make you into the bad guy than to deal with the fear. All you can do is sympathize and let her know that as hard as it is, you have faith in her intelligence and sensitivity for dealing with it.
If taking charge of this situation is too hard for you, I suggest you get a counselor for yourself to give you the support you need. You deserve to have a life that isn’t centered on your sister’s problems.
I wish you well.