This is the 9299th most frequent Japanese word.
百合子
"百合子" (Yuriko) is a feminine Japanese given name meaning "lily child."
In this sentence, '百合子' is a proper noun used as someone's name, indicating the subject of the action.
百合子は図書館で本を読んでいます。
Yuriko is reading a book at the library.
Here, '百合子' is again used as someone's name but with 'さん', emphasizing politeness and respect when addressing the person.
百合子さん、こちらへどうぞ。
Ms. Yuriko, please come this way.
In this context, '百合子' is a possessive noun indicating that the opinion belongs to Yuriko.