Depending on the age of your house, it could be another spirit, but as was already mentioned by Black Tail, check for the mundane, normal explanations first. I went to an exorcism once where the supposed spirit was a raccoon in the walls.
Also, spirits tend to stick to places important to them in life, or to where they died. It seems unlikely that this girl would go after you, unless you unknowingly walked by her body before it was found, in which case she may have followed you since you seem more sensitive than most. Happens to me all the time, the bad part of being so grounded by my earth wavelength.
When I walk in your dreams you will find only peace.