Leah Sharibu was one of 110 students kidnapped by Boko Haram from their boarding school in Dapchi in February last year.
While all other girls have been released - it's reported her captors have kept hold of Leah because of her refusal to convert to recant her faith.
According to religious freedom charity Aid to the Church in Need, her mother Rebekah said: "I know that all over the world believers are praying and advocating for the release of my daughter, but until now I haven't seen my Leah.
"I want to plead that Christians do not get tired of praying for her until she returns."
Nathan Sharibu, Leah's father, said: "My daughter's trust and faith has made me realise that I have been living under the same roof with an admirable disciple of Christ.
"I am highly encouraged by her strong faith in the Lord and her refusal to renounce Christ even before death at the hands of Boko Haram."
Earlier this week, Premier reported how attacks on Christians in Nigeria were set to increase in 2019.
Religious freedom charity Release International called on the UK government to do more to put pressure on authorities there.
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