Isn't that a bit harsh. Getting rid of her without asking her why she is there! she could be a murder victim asking for your help then you just say F off and get rid of her. Try talking to her, communicate, as long as she is not violent or intrusive I would try to bond with the spirit.
or she could just be an imprint, like a video on a loop, a memory from something that happened there long ago. If she dose the same thing over and over it is likely she is an imprint.
If you still feel like getting rid of her is the best thing to do, Try the Lesser Banishment Ritual of the Pentagram. I think it's on this site, If not, it's on the Golden Dawn's page.