Ms Gardner said they had tried unsuccessfully to get tickets in the summer and it came out of the blue when Mr Taylor announced he had been able to secure some just a week before the show.
During the performance, she said Sheeran had announced he would be playing one of his new songs and invited the crowd to film it.
“I sort of nudged my now-fiance and said ‘film it then’,” she said.
“Then all of a sudden I was listening to this song and he’d just passed his phone to a stranger and I was so confused. Then obviously he got down on one knee and asked me to marry him.”
Ms Gardner said it had nevertheless been a risky move, explaining: “I always said I wanted to get engaged abroad so it was a massive shock, but it was honestly absolutely perfect.”
After she said “yes” to the popped question, she remembered “all the people around us were so kind, so nice”.
A number of people filmed the proposal and then offered to send her the video afterwards and she said friends and family had also been “over the moon”.