She pretty quickly forgot David was the one who wanted to freeze her to take the alien home ala Burke from Aliens.
She'd literally gone straight from the surgery to discovering Wayland (with David being nice and putting a coat over her), then less than a minute later learning "One of [the Engineers] is still alive - and we're going to meet him." Yeah, I'd be pretty distracted myself at that point.
And again, that scene made it pretty clear that Wayland, not David, was the one pulling the strings and calling all the shots. And she considered David a mere machine with no free will of his own who HAD to follow his creator's orders. She accepted David's aid at the film's end because 1) she had no choice if she was gonna live (and vice versa with David) and 2) She was now David's master and he had to follow HER orders.