Lisa Bridgett, of Pwllheli, had been using the phone after the Ariana Grande concert on Monday when the explosion caused a steel nut to hit her.
She lost a middle finger before the nut went through her phone and her cheek, ending up lodged in her nose.
Her husband said the phone probably diverted and slowed down the nut.
The bomb attack at the Manchester Arena killed 22 people and injured a further 64. Eight men are in custody following the attack, carried out by Salman Abedi.
Mrs Bridgett, who was at the concert with her daughter and her daughter's friend, was in a "positive mood" and felt "very lucky to be alive", her husband Steve said.
She had surgery on Tuesday and was due to have another operation on Thursday after suffering multiple injuries, including a fractured ankle and a large wound on her thigh.
"The fact that she was on the phone at the time probably saved her life," said Mr Bridgett in a Facebook post.
"The nut has hit her phone which has more than likely not only diverted it, but also slowed it down considerably," he said.
Mr Bridgett said the couple were keen to thank police and hospital staff, as well as a steward called Peter "for helping Lisa outside and getting her to safety".
Pictures have emerged showing a mobile phone which is believed to have saved the life of a Gwynedd woman badly injured in the Manchester bombing.