Americans grow up in an environment that encourages people to "express themselves" and such.
Her parents are Japanese and Haitian:
Two cultures where freely "expressing yourself" are frowned upon. Especially haitian culture where, as they always say ,
" children are to be seen and not heard" so she's bound to show restraint with her emotions.
In many cultures, when you marry a woman, the man takes the woman's last name. So that could be it too if Japanese culture is similar.
Go to Brazil and marry a Brazilian woman and see what happens to your last name. GONE.