A thing on the film Lars and the Real Girl

Socializing hurts Lars, but through a co-worker he learns of a website that sells life-like sex dolls, so he orders one and, upon her arrival, makes her his girlfriend. To him, she poses no threat. She can be his creation, and from her he creates a saintly Brazilian missionary immigrant named Bianca who, being wheelchair-bound and having a limited understanding of English, is completely dependent upon him.

But soon other townsfolk co-opt his creation, and they make Bianca more dynamic, resourceful, and, eventually, independent. Lars originally used Bianca to approximate intimacy; with her he could relate to the world the way he wanted to be related to--with patience and sensitivity, without possibility of rejection. But suddenly realizing he is no longer Bianca's only connection to this world, thereby feeling rejected, Lars defiantly sets out building connections of his own by going out with a young lady he works with. From there, we put Lars on the road to deliverance from the prison of his inhibitions.

The movie feels sweet, but underneath is a careful power struggle between Lars and the town. Lars' truth is dubbed a delusion, and soon others' truths are being imposed from all sides until Lars, having lost control of his creation, announces that Bianca has died--a final and dramatic act of self empowerment. What is it exactly that either pushes or inspires Lars to change, to conform to the town's normalizing desire for him to be more social?