Demon or Ghost in My Sister's Bedroom

This is a true story as per my sister who's nickname is "Mars".
First of all, I am a skeptic when it comes to ghosts and demons, although I do believe demons exist, I do not believe they can come into this earthly world to hurt or torment us.
A few years ago, prior to this incident taking place, I went to my church which is not too far from where we live, and summoned a priest to bless our newly purchased home, not because it was haunted, priests just do that for new homes, cars, pets, etc.
The day he went to bless the house, my sister had locked her bedroom because she had stated it was messy, therefore, the priest, Fr. Paul, was not able to bless her bedroom. I do not remember how long ago from the day Fr Paul had gone to bless the house, when the incident that happened to my sister occurred in her bedroom.

One morning, she had woken to find bruises on her which my mother thought were caused from a fight. My sister tells the story:
"It was night time and I was lying on my bed, on my stomach. I had the sheets off, touching my feet, at the edge of the bed, suddenly the sheet covered me entirely and I couldn't break free. I was trying to uncover myself and when I finally was able too I was gasping for air."
She had told us about other times where her stereo would turn on and off and the lights would turn off by themselves. I, of course, always tried to find explanations for those occurrences.
I told her maybe there was an outage or something wrong with the wire. Her and I had the same AIWA stereos, one in her bedroom and the other in mine. Anyway, the night she was covered, was the time she had those bruises. I told her she might have been dreaming and hurt herself. She claims she was awake the entire time before that happened. She said there was a demon or ghost which she named Frank. Why? I don't know.
My mother got some holy water from our church and a scapular and a cross. When my sister has these experiences, she grabs the holy water and yells cuss words at "Frank" and she says he stops. For the past year, she has not reported any incidents and does not know why she was haunted and hurt by "Frank". She wonders if the priest had blessed her bedroom, maybe she wouldn't have had this and other occurrences she has had in the past.
As a child, she stated to have seen the devil and have felt heat. She is now 22 yrs old.
I am really into the paranormal and ghost stories, etc. yet I still question it all. I guess because I have never experienced anything like the stories I have read on Castle of Spirits and certainly nothing like what my sister has experienced.