A Doppelganger Of My Classmate

It was Saturday morning. Some of our classmates, including me were task to go to school to finish our "Beautification Project". We were done exactly at 11:00 am. All of our classmates (excluding Trisha, Karen, Ariana, and me) went home. Ariana told us to wait here at school while she will go and buy something to eat (She didn't eat breakfast). We agreed so we waited for her.

Since there's nothing much to do, we decided to go on "Ghost Hunting". We went up to the second floor and began filming all around us with Trisha's phone while walking. As we passed by the Library, we all felt a very cold wind around us. Trisha screamed "Takbo!" (Run!), then we ran outside the gate and we saw the guard. The guard is very angry with us and told us to go home. 

We text Ariana to go to my place after she is done eating. At my place, we replayed the video. As the film passes by the library's glass window, we saw "Karen's reflection wearing a blue t-shirt" in front of Trisha. Trisha was so shocked and said "Diba nasa likod ka Karen? At diba nag-susuot ka ng puting T-shirt kanina?" (Wait! You're at my back, right? And are you wearing a white T-shirt back there?) Karen said "Oo, ba't naman ako nasa harap... Diba ikaw yung palagi nasa harap? At Oo, hanggang ngayon nagsusuot parin ako ng puting T-shirt!) (Yes! Why will I be in front? Clearly, you're the only one who is in front, right? And I'm still wearing the exact same white T-shirt) We tried to replay it again and again and still the same. 

Is this really a Doppelganger of my classmates? Please, I really need help. Any suggestions or advice guys?

Source: yourghoststories.com