Amanda is a really underdeveloped character. Her relationship with Kyle seems to be written for a Disney Princess movie, not a show with an audience above 12.
The idea of Kyle+Amanda is appealing: Love from first sight, Kyle=prince charming, an attractive, intelligent guy whose life revolves around making her fall in love with him (unless he is out saving the world and curing the sick). He is essentially the perfect boyfriend.
Amanda=the typical girl next door with a good heart. Many people identify with her and thus want her to have her "prince charming".
The problem with this relationship is that it is downright boring. After the first date, there was really nothing going on. Ever. Even though I have watched the series over an embarassingly short period of time, I do not remember them ever doing anything other than staring longingly into each other's eyes. If Jaime did not come along the show would die in the beggining of season 2.
Jessi on the other hand is a much more complex character - and Jaime does a superb job portraying her.
The fascinating thing about her character is that she wants nothing more than to be like Kyle. She wants to be friends with the same people Kyle is, she wants to be liked, she wants to be "special", to be the prodigy Latnok is searching for - all the things that Kyle has and takes for granted.
What makes it even more interesting is that she is the only person Kyle is somewhat of a jerk to for most of season 2, throughout the show his lack of regard for Jessi´s feelings is his only imperfection.
He realizes that he is the only genuine friend Jessi has (on several ocasions) , yet he keeps turning her away to be there for people who do not truly need him - most of his time is spent tutoring people/making dinners/fixing household appliances etc, but he does not have enough time for Jessi and almost drives her to a point of suicide.
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