Not realistic at all.
I'm not even talking about immaculate conception here. Let's talk reality, mormon girl goes off to las vegas, doesn't get raped? Incredibly lucky this girl was really gullible with no common sense to aid her. She also stumbles over her long lost father conveniently. Because this happens all the time. You just stumble over your biological parents. Why is her bio dad so accepting of her boyfriend? He doesn't feel the least bit preoccupied for her safety with this dude? Hard to believe. She's 15, didn't her bio dad just kidnap her from her mother? Can't you only get married with consent of your parents when you're underage? It was kind of absurd that she believed the tape got her pregnant but obviously I have to let that slide. She doesn't seem to know a lot of things as a mormon.
Overall a good film but I had to pretend like any of this could actually happen for an hour and a half. That was hard to do. I liked the dialogue. Aiken and Culkin gave good performances its a shame I want to see more from aiken.