To what extent is the statement true that the envious person is not included among those intended by the noble verse: "Repel [evil] with that which is better; then verily he whom between you and him was enmity [will become] as though he were a devoted friend," and that the way to deal with him is by keeping away from him and seeking refuge in Allah, not by kind treatment?

The envious person is an enemy, even if they do not show their animosity. They may be more harmful than an open enemy because overt enmity or conflicting interests can cause envy, but not always. To cure envy, Allah Almighty has guided us to repel evil with good: "Nor can goodness and evil be equal. Repel (evil) with what is better: then will he between whom and you was hatred become as it were your friend and intimate!" (Qur’an 41:34). So, kind treatment and benevolence towards the envious person extinguish the fire of their envy and transform animosity into affection. Thus, either they are enslaved by your kindness, or their heart is shattered by their persistence in ill-will.