Haunted Room?

I was visiting my dad the other day and we were talking about my sister who had recently visited a medium and was apparently contacted by the spirit of my grandmother. Lo and behold, my sister walked in the door, so I began to pick her brain about the medium experience. Well the conversation strayed to how she had been visiting graveyards late at night as well as going on ghost hunts to see if her and her friends could find any sort of haunting in the Greater Knoxville area.

The first thing my stepmom says is, "Have you been using sage or anything to cleanse yourself?" My sister replied that she had not, but that she did use salt. We both remarked that we had never heard of salt ever being effective. I warned her how I thought (and I may be wrong) that she may be leading spirits back to my father's apartment without even knowing. She replied that she did not feel that was the case and that she didn't see any potential harm that could come from visiting graveyards.

However, she goes on to mention that every time she walks by my old room, she gets "a really really bad feeling". She also mentioned how her boyfriend had said the same thing to her without any sort of prior conversation, just that he always felt very uncomfortable walking by the room.

I was very shocked at this. I had stayed there as recently as this summer and don't recall any sort of feelings of fear or anything besides maybe once or twice. I did always have trouble sleeping at night there, but I attributed that to early morning classes and my tendency to take naps. I honestly have never felt the room was haunted.

So I feel like there are possibly two explanations for this. Maybe my sister's boyfriend gets a terrible feeling when they walk by my old room because he knows I don't like him, and how overly protective I am. But... Does anyone think it is possible that perhaps my sister has brought back some sort of spirit (s) that might be residing in there? I feel like her hanging out at graveyards and whatnot without any regard to cleansing herself is just a recipe for trouble. I'm curious as to what this could possibly be, and any potential steps or precautions that could be taken. I'm a little freaked out about it, especially as I had planned on staying with my father frequently over the summer.