A really bad feeling about a person...help?

Okay well there is this girl and id rather not say her name so ill jus refer to her as Stacy and ive been getting really bad feelings about her as i got to know her more. As we grow closer, the feelings grow worse and i hate it! Here's the story and it'll explain why im asking for help here instead of my friends. Okay well theres this dude and id rather not say his name so ill call him Fred. Well anyways me and Fred went out and everything but when we broke up we became even closer as friends. Me and him are really close but i ended up falling in love with him and i havent stopped loving him since but im already trying my best to get over him. Anyways, me n Stacy weren't good friends then so the feelings weren't as strong but were still there. She told me she liked Fred and Fred told me he liked Stacy so becuz of me i ended up hooking them up, thinking it would make them both happy and maybe tht bad feeling would go away so i thought it was a win-win situation for all of us, in the end the feelings grew even worse n it was starting to get hard to be around her with the bad feelings and not say anything to her about it. And becuz of her, me and tato still hang out alot but we dont really talk alone much anymore. its been a month since we hav and we would usually do it every other day sometimes days in a row. Stacy is always going in between me and fred whenever i try to talk to him about something serious n i feel as if she is completey trying to get me away from our friends. i understood at first when she was jus doing it over fred but then she did it over all of our friends and everytime i try to talk she would do something making her the center of attention n now im completely ignored in our group of friends and i hav to do something outrageous jus so i can get a word in. Stacy is one of those girls tht a person cant help but "love" is what everyone says about her. everytime our group of friends is hanging out at our other friend's nicki's house, she would also do something so tht way everytime she would get attention. i could tell when or not she was lieing from her eyes cuz its easy for me to determine tht stuff n she was lieing every single time about something tht made everyone feel sympathy for her including myself, but i always had my guard up about it. everytime she does this, the feelings get worse and worse and they arent emotional feelings either, they are feelings screaming at me telling me there is something not right about her. tht shes not who she says she is. i cant tell my friends about this cuz they would say "oh its just ur feelings about fred making u feel tht way about stacy" but its not!!! these feelings were there even before stacy and fred went out, they jus werent as strong, and they started getting stronger before they went out. but all my friends would jus say its cuz of my feelings for him tht i feel these feelings. i did a bit of investigation cuz i even thought i was a bit paranoid but im not. she has everyone wrapped around the palm of her hand. n when i went further to see how much ppl adore her and would do anything for her the feelings just shouted at me saying "shes not what she seems! she's not right" please help me! these feelings are getting worse and worse over time n i wanna do something about it. if ur gonna say its cuz of what i feel toward fred i can tell u without a second thought tht ur wrong cuz its not. what do u do when u get tht bad feeling about a person? i wanna expose her for it cuz i dont want my other friends suffering becuz of her n i forgot thts part of my feelings, she gonna make ppl including our friends suffer, help me please and why am i getting such strong bad feelings? ive had bad feelings about other ppl but not as strong as this. someone please help me! what do i do?