Who is the antagonist in The Notebook by Nicholas Sparks?

Allie is a young girl who is easily swayed by her parents and their decision that Noah isn't the best choice for her life partner. After she and Noah part at the end of the summer, her mother withholds Noah's letters, and it's only later that Allie's mother recognizes the love for what it is - deep, abiding and true. When Allie is faced with the decision to marry Lon as planned or to disappoint everyone in order to marry Noah, she knows that the easiest route in terms of the number of people impacted would be to simply go through with the marriage to Lon. She also knows that it wouldn't be fair to Lon and it seems that this point plays a role in her eventual decision. A further conflict is added when Allie discovers she has Alzheimer's disease.