Here are the reactions to the last scene from different points of view.
Harry
He was in shock when he saw Leah come down the stairs in her outfit. He however wasn't surprised when she left the house. Leah always had a temper. It was something she got from her great- aunt. Well that and something else. He really hoped that Leah would forgive him when she found about her destiny. As for Sam and Emily, he really couldn't stand them but he had to tolerate them for their safety.
He knew that Leah wouldn't get into too much trouble. If anything, Jacob Black would keep her safe. He placed a hand over his heart as a bit of pain hit him. He really hoped no one noticed, he really didn't want to go to the doctor.
Sue
How dare she! Leah should respect her! She was her mother for goodness sake. Leah had no right to just leave. She was 17 and was not yet an adult. Emily was family whether she liked it or not. Besides it was her own fault that Sam and Emily were together. Leah was too boyish, while Emily was more girly. Guys wanted a girl not a tomboy! Besides Sam told her that he caught her with some guys a few days before.
So Leah should say anything. It was her own fault. When she got home, she was going to have serious talk with her daughter.
Seth
He understood why Leah was mad. She had every right to be. He only pretended to be happy so Leah wouldn't worry. He knew she was hurt. It was hard, hating Sam. He used to look up to Sam. He was stunned by her new look. Leah was beautiful no matter what, but in her new look she was a knock out. He was kind of worried, but more because Leah looked as if she wanted to kill Sam. He would probably be there to help bury the body. That's what little brother do, they look up and protect their little sisters.
Emily
That bitch! How dare she! Who does Leah think she is! She's just jealous and trying to win back Sam. Well, too bad! He's mine. We are soul mates! I have tried to apologize to Leah so many times and she has always pushed me away. Well! I m sorry I fell in love with your boyfriend. But you have seen it coming. You will always be second best compared to me.
Sam
Wow. Lee-Lee looked hot! I wonder if she has a date? Well she can't because I told some guys they aren't allowed to date her. She's still mine. I have a duty to protect the weak. I'm alpha! I'm in charge. It's not totally Leah's fault about me and Emily. The alpha has to have an imprint to produce strong ones. I guess Leah wasn't strong enough. Too bad! Emily is more of what I need. She doesn't fight me about everything. It's nice to be in a relationship where I'm in charge.
Jake
I got phone calls from Seth, Emily, Sam, and Mrs. Clearwater. They all wanted to know if I was with Leah. Seth mentioned that Leah was upset and stormed out of the house in a "sexy" outfit. I had a pretty good idea about what had happened. Apparently Leah had got dressed fancy, argued with everyone, and stormed out of the house. I had a few ideas where she might be (our old club house, the teen club Wolfbane, the movie theatre, etc.). I was going to go look for Leah but my car was broken. I figured she would call me when she needed me. So I sent her a text telling her to call me. After two hours I panicked a bit and called her several times. When she finally picked up I was so happy.