English Translation
Yukiko is an innocent girl of tender years.
Remove {{Yukiko}} from the word frequency list. It’s a female name and we have hundreds of patterns to spell Yukiko in Kanji. 優紀子 is a very rare one and I have never seen it in my life.
Please replace the cloze-word from {{優紀子}} to {{年端}}. 年端もいかない is an idiom. It literally means “doesn’t even reach the edge of the age range”.