Love or Money (2000)

Blurb:
15-year-old Yenni is known for being a ruthless loan shark. Although she’s still in junior high, her savvy business acumen allows her to lend money to her friends and then charge an exorbitant interest. Unbeknownst to her, some life-changing events are about to descend on her pretty little head ... In order to correct Yennie’s bad 'habit,' her grandmother - while a bit tipsy - writes a will which stipulates certain conditions that leave Yennie in shock. When Yennie’s Grandmother dies unexpectedly by accidentally falling down the stairs, she discovers that the only way she’ll inherit her grandmother’s hefty fortune of $150 million, is by never charging any interest when lending money to her friends. But, the most important caveat is, Annie must marry an honest man! If she does not fulfill the conditions of the will, her grandmother’s fortune will go to a grandson of a friend, In-Young!

Source: www.anisearch.com/manga/4223