Sandy is beginning to mature... (Para. 22)
Meaning: Sandy is growing up.
mature: (1) vi. become an adult; become fully developed
The oldest child in a family often matures quickly, learning early to take care of the younger ones. 家中最大的孩子往往懂事最快，很早就学会照顾弟弟妹妹了。
(2) a. grown, fully developed
Mature plants grow more slowly than young ones.成熟的植物比幼苗长得慢。