All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
In principle, Nams (plucking the eyebrows) is forbidden in Islam and is considered a major sin. It is impermissible for women to remove hair from their eyebrows without a legitimate necessity. Having stated this, there is no harm in removing a part of the eyebrows if they cause an obvious deformity to the person's appearance in order to ward off this harm.
Allaah Knows best.