Search Results: two guys fighting over you

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My blonde girlfriend came back from university to visit me and her parents and she found a long brunette hair on one of my pillows.
She was furious about it and thinks I am cheating on her now. I adamantly denied this but she didn't believe me and said she was going to search the bedroom to make sure. I said 'go on then' knowing I had absolutely nothing to hide.

After doing her own female forensics she unbelievably found another two brunette hairs in my room. One dark hair was under my bed and another in my sock draw right at the back.

I have two explanations for this….
1) The hairs belonged to either my mom or sister (both however have been away travelling Asia since mid June unfortunately).
2) The hairs could be 1-2 years old and belong to one of my ex girlfriend's…

I've tried explaining both of these theories to her and she refuses to believe either. She is accusing me of sleeping with one of my work colleagues who has black hair and recently added me on Facebook.
Anyway she went back to her parents house crying yesterday and hasn't replied to any of my texts or calls since. I don't know how to prove my innocence and I am fighting for my relationship here, that's if it isn't already over. I definitely haven't cheated! Please, I need help here. Is she being irrational or would you have trouble believing me too?

Most of you know my story...
We were co-workers, from India
At first she had some sort of attraction and interest in me. we started of well. she didn't knew my age at & am younger to her.I caught her staring at me more than once. she locked eyes with me. when i was having lunch and i turned around by accident to se she was starting at me cold stare for 10 second. before i turned around. she gave out her number to me. she added me on FB. she even invited me out alone only two of us. at the end of the day wen we hungout, she asked me " i will bring u cooked food will u eat it for me?" i was over the moon. after three months like this,
Now, she knew i am younger than her by 2 years. one saturdayday she asked me helps and i asked her shall i give it to u near ur house so we can meetup. she said yes. i went near to her house and called her. she said can u come near my house. i went there. she invited me inside to come in and she introduced to her parent and she was like i told u that guy. he is... we had good time with her parents and her dad was a cop. she flirted me infront of her parents. her mom was staring at us like cold stare. we had snacks at her home.
exactly a day later, she called me out in person and said "my parents instructed me not to encourage boys to send smses and calls. so pls stop calling or msging me, cause if they say somethng it will be for my good. Also, my parents are lookng out for marriage alliance" i said no issues i like u btw. can u spk to ur parents for a possible alliance btwn us. She said like "I am older than u and my dad is old fashioned and won't agree my husband younger than me" i can't take this frwd knwing they won't agree 100%. i didn't pressured her and left off and waited for her to change her mind for 5 months.
Now
she is engaged to a guy as per her parents wish. arranged marriage. But i see her feelings for me in her eyes. i catch her staring at me, she care for me.

My girlfriend and I met just about a year ago and quickly began dating. She lives almost two hours away from me and we are both college students, but we have made it work so far and we have had the most amazing times with each other.The happiest I've ever been is when I'm with her.

An important piece of background: my girlfriend and I have always been great with communication, and keeping literally nothing from each other. However a few months back (dating about 5 months) I noticed she had been messaging another guy over fb (From a different country telling him that she loved him, they had met when she went on a school trip). After a short break in dating and some promises from her, and many, many tears on her end, I saw a change in her as a person and eventually took her back, and everything has been amazing since, and all that trust was built back up over the following months.

She has been in the study abroad program (living in London for 6 months), and has been very loyal to me since this first incident. Hasn't danced with any other men, texts me every single night and morning etc, sends me letters, skypes with me, I even got to go visit her for a week, she has been the definition of a perfect and loyal girlfriend...However yesterday she had come back from a trip to Italy and told me that another man had kissed her, and she kissed him back (she was also sober, and this man was a stranger she met at a train station, it turns out he walked her back to her dorm and kissed her at the door, and she allowed it).

Since then I blocked her from Skype, text, every means of communication we had. In the past two days she has written me a song, apologized a million times and has shown true regret, and also gave me a 45 min long slideshow of pictures from literally EVERYTHING we have ever done together. So, it is blatantly obvious she still loves me. She tells me she won't ever stop fighting for me.

Should I let this slide and take her back, or call it quits?