Hi, there.  If she were my daughter, I would probably get an evaluation from a psychologist.  They could also tell if medication might help, as well.  If she's had symptoms this long, chances are that it's depression.  I've been through this with both of my sons, who are now grown men; one of them had even lost 25 pounds and I didn't even realize it until they got him on the scale.  I think it's better to be safe than sorry - getting an evaluation will clear up any doubts and maybe clear up some things.  Good luck and I think it's good that you're taking the initiative.  We hear from a lot of young people who want to get help and are afraid to tell their parents.  Let us know if you need any other information.  Thanks for reaching out.