A young Christian girl whose father died in a bomb attack carried out by an Islamic extremist on a Coptic church holding a Palm Sunday service has shared how her faith has grown stronger amid tragedy.

Marian, a 15-year-old Coptic Christian, recently told persecution watchdog Open Doors how her father, Nabil, died in her arms after an ISIS-linked suicide bomber entered the service held at church of St Peter and St Paul in Cairo. The December attack left 25 dead and dozens injured, making it the deadliest attack on Egypt's Christian minority in years.

That Sunday, just days before her 15th birthday, Marian went along with her father as he guarded the church. "We had breakfast together, and we were joking with each other," the teen told the outlet. "He was exceptionally happy that day."

After the first service, Marian's father asked her to go home and bring some tea: "I had just started the water cooker when I heard a big explosion. I thought of my father immediately," she recalled. "There was white smoke everywhere, and people were running around in panic. I was in shock, but I managed to run outside. I started asking everyone if they'd seen my father."

Through the smoke, dead bodies, and blood, Marian saw her father lying near the entrance of the church.

"He was just lying there, still holding tight to the keys of the church, even though the explosion had blown him meters away," she said. "I put his head on my lap. He gave me the keys and asked me to take care of my younger brother and sister. Then he closed his eyes and smiled peacefully, his face shining. Then he went to heaven."

After her father's death, Marian struggled with a range of emotions, from anger to sadness to disbelief: "My father was a great man, a loving father, I missed him so, so much. I asked God why?" she recalled.

Now, nearly a year later, she says that while she physically misses her father, she doesn't feel like he has left her. "I believe he is encouraging me from heaven to live close to God," she said. "I feel like he's telling me that I'm not alone, that Jesus is with me."

Marian, her mother, and younger brother and sister continue to live with their family on the church premises for now. She hopes to one day become a doctor - like her father wanted her to be.

"And I go to church now each Sunday; my faith has grown," she said. "I don't know what tomorrow will bring, but I do know that God will take care of me. I have felt God's incredible comfort through these times. And I've felt the warm love of the Christian community. God takes, but He gives back more. I can't repeat it enough, and I want the young adults around the world to know it as well."

"God is love. God is kind. God is merciful. I have experienced this in my most difficult hour."

Egypt President Abdel Fattah el-Sisi said that it was 22-year-old Mahmoud Shafiq Mohammed Mustafa who entered the church attached to the St. Mark's Coptic Orthodox Cathedral and detonated a 12-kilogram explosive that killed mostly Christian women and children. He described the attack as an act of terrorism and declared a state of mourning for three days across the country.

The Islamic State later claimed responsibility for the attack and issued a statement that identified the suicide bomber.

To this day, the church has not covered up evidence of the attack in an effort to remind worshipers of the martyrs who sacrificed their lives for their faith. Dents from the blast can be seen on the pillars and walls of the church.

"The church didn't repair them on purpose, so we remember how the women died for their faith that day and how my father, as the only male victim, died as well," Marian said.

Coptic Christians account for about 10 percent of Egypt's population of 82 million.