The singer was apparently holding a bedside vigil for 68-year-old Rose - who helped raise her - before appearing at the ceremony.
Adele cancelled all other commitments following her grandmother's collapse in a South Wales supermarket, The Sun on Sunday reports.
"Adele was panic-stricken. It would have broken her heart to have lost her. She didn't leave her side until doctors reassured her that her gran was on the mend," a friend said.
Rose is now recovering at home in Penarth after surgeons widened her arteries with two stents.
ITV recently apologised to Adele after cutting short her acceptance speech at the Brit Awards.
Watch Adele in the video for 'Someone Like You' below: