She is more of a romantic figure in the film and much more of a manipulator, of the 3 men in her life, in the novel; Frankly, that makes her more interesting.
"It's the system, Lara. People will be different after the Revolution."
The novel's Lara is a much stronger person than the movie's Lara; physically as well as mentally. Examples: A) She willingly estranges herself from her mother and brother and goes away to work as a nanny just to extricate herself from Komarovsky's hold. B) When Yuri visits her at her house in Yuriatin she is carrying two pails of water up a staircase. When he offers to carry them for her, she politely refuses, saying that she always finishes what she begins.
That's why it is more believable that Yuri would instantly feel a mysterious connection and attraction towards her at first fleeting sight. That's also why Pasha and Komarovsky want her as well.