Her Parents Are Tribalistic.

Dear Amara, God bless you for your Good works.
That exceptional grace God has given to you will never leave you but increase rapidly.
I want to share something going on with me with you. My relationship is just roughly a year with my girlfriend but we have been very close as friends in almost three years before dating. I work in lagos while she works in ogun.
A week into our relationship, she visited me to tell me something very disturbing. That she was bored one certain evening that same week and she had to unwind, so she went out with a guy, from the outing to his apartment, she cheated and she insisted there was no sex but it was a mistake.
Didn't go down well with me but I forgave her after a while to see what was ahead. The fifth month, I went to check her up at her house in Abeokuta only for me to see her parents also visited, they came from Lagos too.
Her parents were seeing me for the first time but have heard so much about me so they took me in with joy.
After some nice conversation her parents asked a sensitive question about my origin which I said I am from Enugu state.
Immediately I was told to get out of the house that they don't want to ever have any Igbos around thier daughters cos they are from ondo state.
I had to speak to my girlfriend seriously about it and she said her parents are tribalistic but she doesn't care about what they say but about her decisions.
After a while, I discovered she changed in communication, she won't return missed calls or reply messages, when I ask why she will tell me she ran out of airtime.
I kept it cool. She came visiting last weekend,  somehow, I noticed a close conversation with another Yoruba guy on her calls and I asked her who this guy was, she kept saying a friend.
When I did my investigation (bbm, whatsapp, sms), I noticed she has been seriously hanging out with him both in his house,  and bars in Ogun state.
Asked her again and she said nothing.
I am already taking a decision to end the relationship. What's your advice. Thanks.

This must be trying times for both of you and whatever decision you take with respect to this is only what you feel is best and within your limits of endurance and love for each other. 
For her she may be weak or not encouraged to manage her parents perception of her partner with maturity, wisdom and patience. 
It could be a case of her needing much more assurance and support to enable her talk with her mother and plead with her father to bless her marriage with you. 
It could also be that she has already given up and she's shopping for a replacement somehow even though she is convinced of her love for you. 
On your own part, her parent's reaction maybe a test of how genuine your love for her is. It may also be a test of how much you can endure to be with her. 
No matter the perception and the opinions of parents about a partner, they can't help but give their blessings whenever they see couples who are consumed by love and selfless devotion. 
It's a mystery beyond life and one that no parents can hinder no matter the tribe and tongue. 
This is not an issue of her chats and calls but that of your convictions and your passion for your partner and how much you are willing to endure to be with her. 
What her parents did that day could have weakened her and disturbed your heart but is that enough reasons for you to back out and end your relationship with your partner? 
I feel that taking another step of faith this time to visit them officially will soften their heart and with the support of her siblings who should know about your journey, her father wouldn't have any other option but to bless you. 
But like I said, it's your journey and you know exactly what you need in a partner you desire to spend the rest of your life with. 
If she doesn't have those qualities and you feel that she's not the one God has made for you, then do well to terminate the relationship and trust God to give you the partner who will be there for you. 
Love conquers every limitations of life and with patience you shall always possess your possession.