She is taller than her two sisters.She is the taller of the

She is taller than her two sisters.She is the taller of the two sisters.
这两个句子有什么区别吗?
第二个句子有没有错误啊?该不该将the taller改为the tallest?
感谢你从百忙中抽时间来浏览或是回答我的问题.thx so much.