Her husband Paul Charman spoke to the Herald from Auckland Hospital soon after the incident as his wife was treated.
He said Christensen was left bleeding and wedged against the wheel of the bus after the collision.
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"She doesn't remember what happened after that because she was knocked out cold.
"Her head was under the wheel of a bus, that's how bad it was."
He said his wife, who is a keen mountain climber and adventure-lover, had lacerations to her face and skull.
A passenger on the bus called 111.
She said the young male scooter rider was "very shocked".
The day before Christensen was injured a 59-year-old man died while riding a Lime scooter along Fanshawe St.
The man died of natural causes.
But his death is the first connected to the controversial e-scooters in New Zealand.
On Tuesday night another person suffered life-threatening injuries in an e-scooter crash in Auckland.
As of midday Wednesday they were still in a critical condition, an Auckland City Hospital spokeswoman said.
Auckland councillor Christine Fletcher has previously called for "a complete review" of the e-scooters in a bid to introduce tighter safety regulations.