Meaning:

“扶” means “to support,” “弟” means “younger brother,” and “魔” means “monster.” Chinese netizens coined the term with the same pronunciation as the Chinese for Voldemort, the evil English half-blood wizard from the “Harry Potter” series of books, for a comic effect. It refers to elder sisters from families where male offspring are much more valued than female. Brought up in such belief, the elder sister tends to do everything she could, even at the sacrifice of her own interest, to help and support her younger brothers.

Example:

A: 小花怎么又吃方便面了？

Xiǎohuā zěnme yòu chī fāngbiànmiàn le？

Why is Xiao Hua eating instant noodles again?

B: 大概这个月的薪水又给弟弟了，她真是扶弟魔本魔。

Dàgài zhègeyuè de xīnshuǐ yòu gěi dìdì le，tā zhēnshì fúdìmó běn mó。

I guess she has given her salary this month to her younger brother again. She just does everything for him, totally neglecting her own needs.