The 29-year-old doctor and her new husband, Ahmad Subeih, 34, are now still struggling to process what has happened to their home city.
Instead of a cherished memory, the couple's wedding video now serves as high-definition documentary evidence of a tragedy that killed at least 135 people and injured more than 5,000 .
The President of Lebanon, Michel Aoun, has said the blast, which occurred around 6pm local time on Tuesday and was felt as far away as Cyprus, was caused by 2,750 tonnes of ammonium nitrate being stored unsafely in a warehouse in the port area.
It destroyed much of the city, with aid workers flying in from around the world this week to help in recovery efforts.
Hospitals in the city, already struggling with the coronavirus crisis, quickly filled with the injured.
Ms Seblani, who rushed to help the injured nearby after the impact, told Reuters: "When I woke up and saw the damage that happened to Beirut, the one thing I said was thank God we are still alive.
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“What happened during the explosion here - there is no word to explain ... I was shocked, I was wondering what happened, am I going to die? How am I going to die?”
The dramatic footage shows the moment the city went from calm to devastation. Shattered glass can be seen all around on the street outside the hotel where Ms Seblani was to spend her wedding night.
She described the scene at the hotel when they returned to collect their passports the next day as "unbelievable".
The couple fled to the central Beirut Saifi square for safety, and now plan to return to the US where Ms Seblani works.
Mr Subeih said: "We are still in shock ... I have never heard anything similar to the sound of this explosion.”
A national day of mourning was announced in Lebanon to mark the catastrophe.
Up to 300,000 people have suffered damage to their homes, and on Thursday morning dozens of people were still missing, feared dead.