A hook is a reason why a college would want one particular student on campus as opposed to other similarly qualified candidates. Some examples of a hook would be a student/athlete being recruited to play quarterback on the college football team, the child of a huge donor (in the hopes of getting additional large donations), a person whose accomplishments would bring positive press to the school (ex. Malala).
Very few people have hooks. What your D has is an excellent, meaningful EC activity. That is great!
And as a bit of unsolicited advice…your D is a sophomore. Please do not set up Ivy schools as a goal. Admissions rates for the Ivy League and equivalent colleges are generally under 10% and there is simply not enough room for all of the well qualified candidates. Instead, when junior year comes honestly asses her academic stats (including GPA, standardized tests, course rigor) as well as your financial needs and have your D apply to a wide range of reach, match, and safety schools that appear affordable (run a net price calculator for each school) and that she would be happy to attend. There are so many wonderful schools out there where your D can have a great 4 year experience and get where she wants to go in life.