A 19-year-old woman is lucky to be alive after plunging five floors off a Queens rooftop early yesterday as her horrified friend watched, authorities said.

The victim was hanging out with her pal on a building fire escape on 210th Street near 94th Avenue in Hollis at about 2 a.m. when the pair decided to climb up to the roof, officials said.

Some time later, the 19-year-old started back down, lost her footing and plummeted to the ground, officials said.

The teen was rushed to Jamaica Hospital, but amazingly, she is expected to survive, cops said.