Strange beam and apparition terrifies child

I didn't think anything of it until years later. I was twelve or thirteen (26 now) and my sister was eight or nine (22 now). My mother and her live-in boyfriend both worked third shift so they would leave the apartment at about 23:30 or so. They would leave the door locked, the living room light on and the TV going so people wouldn't try to bother us. I was awoken at probably around 00:00 or so for some reason. I didn't know why but it felt that I shouldn't be asleep. I kept having the feeling that something was outside or nearby that shouldn't be. I still fell asleep though. My sister came into my room at probably 01:00 or maybe later, but it was still nighttime and my mother still wasn't home. She said she was scared because she'd seen grammy (our grandmother had died not very long before) and she said grammy had had big eyes and vampire teeth (just bear with me). I mumbled that she could sleep with me. Then, not too long after she woke me up again and she was crying now. She had supposedly seen a blue beam of light CREEP in through the window, touch the wall next to my bed, mere inches from us, then slowly ascend the wall. When it hit the thermostat it darted out of the room and she claimed to smell burning paper or wood. Despite wanting to know what happened and being scared, I fell back asleep. In the morning she told me grammy had come into my room and asked my sister to go with her. My sister asked: "To heaven grammy?" to which the apparition chuckled somewhat darkly and said: "Not exactly." My sister couldn't remember anything after that until waking up. As I got older I began to become interested in many things, UFOs and the paranormal among the subjects and as I learned how many different ways aliens and supernatural forces come into contact with us, I couldn't help but wonder if this wasn't some kind of alien contact. I have heard that many abductees recall seeing familiar images instead of Greys or aliens, but with big eyes i.e. owls and monkeys with big eyes. I just kind of figured I would submit the report despite it taking place years ago.
Date is approximate.  PD