That's why, when she tells Young Ju that "These are my hands" (31.19), it seems so deep (and it is). She means that even though her hands show all these battle scars from all her difficult years, she wouldn't do without those scars because they're who she is.
Hers is a really hard-earned wisdom because Uhmma's definitely not this wise at the beginning of the novel, when she tells Young Ju how important it is to "look like a real Mi Gook girl" (5.39) with curly hair.
In fact, Uhmma's lack of savvy for much of the book is what makes Young Ju seem like the deep, wise one, the one who tells her mother to stop making excuses for Apa's abusive behavior and who tells Uhmma "You have choices" (26.66).
So when Uhmma finally decides to let Apa go out of their lives for good, it's almost like the cosmic order of the novel has returned: finally Uhmma's the mother, and Young Ju's the daughter. Therefore, at the end of the book Uhmma's the one with all the wisdom, and Young Ju gets to be the kid again.
Uhmma's decision to survive as a single mother is also what gives her speech about how Young Ju and Apa are both "dreamers" a lot more gravitas than it might otherwise have. Because she chooses to do the right thing by her kids, it's almost like the author graduates her to Obi-wan-kenobi status, which automatically makes Young Ju (and us) listen to her. How else is she able to get Young Ju to take a picture of Apa with her to college and signal to Young Ju that Apa is still a part of her family, even if a difficult part?
This moment with the picture indicates that Young Ju has some mad respect from her mama—all of which Uhmma completely deserves by the end of the book.
Think of Young Ju as a character with two identities: the rebellious, spunky teenager and the demure, goody-two-shoes. We mostly see the demure, goody-two-shoes side (because she really is a good kid), but it's hard to stay demure when you've got a dad and brutal who's as mean as Apa. But demure she...