Stop relying solely on the spirit to tell you where she is. She can really only give you her last memory in detail, everything else is up to you.
Contact who ever is related to her or contact someone working or who was working on the case and see if you cant get details on her. See if you cant get any readings from pictures.
You know where she is, you just need to know how to get there. Best place to start is find out where she was last seen. You are gunna need to travel. She wants you to find her, so YOU need to find her. When you find the spot you think she is, you need to call in cadaver dogs to look for her remains in the area.
This has thankfully been done many times with empathy and psychics, including children with these abilities who helped find the body of a boy who went missing over a year and a half prior, as well as intuitively know there was other people involved and described them in such a way that the parents knew exactly who they were talking about.
Dont close yourself off to her. She needs you.