So @Rachim suggested I make this into a blog, and it's basically my thoughts on Sam liking Freddie:
This is what I think happened:
Sam has always loved Freddie, but knew he liked her best friend. So she was always rude to him, out of anger and hope that he'd get the message and like her back. When he suggested kissing in iKiss, she gladly accepted because she thought this was her one and only chance. She never stopped being rude to him because she never thought anything would happen between Carly and Freddie and didn't think to change her behavior. But when Carly and Freddie slow danced, she was very upset. But she still didn't do anything about it because she didn't think they'd actually date. Then, when they did, she had to do something. Not only did she love Freddie, she knew Carly would break his heart and that they weren't right for each other. She told Freddie to break up with her, and they did. She was relieved. She didn't change her act because she knew/thought that Freddie still loved Carly and didn't want to cause any trouble. But, after iSaFW, she saw her chance. She knew by then that Freddie didn't love Carly, so she decided to do something. She couldn't bring out her feelings directly because that's just not Sam's nature. She continues being rude and beating him up, but when that doesn't catch his attention, she realizes that she needs to be nice to him for him to notice her. Little did she know/expect, everyone thought she was in love with Brad instead and it broke her heart that no one could see how much she loved Freddie. Then, when Freddie came out to talk to her, she knew this was her last chance. She knew she had to do something. She knew that he was totally clueless to her love for him, and always would be if she didn't do something. So she kissed him to tell him, "I love you!" And now, all she needs, is Freddie's answer: Does he love her?
This is what I think were Sam's emotions these past four years.
Additional: I also think that Sam had a crush on Freddie for the first two years, but after iSpeed Date, she knew she loved him. She also believed he would never date her because he liked Carly. But after iSaFW, she realized that she had a chance with him.