The feminine term is the general designation of all whom James here rebukes. The apostate members of the church are figuratively regarded as unfaithful spouses; according to the common Old-Testament figure, in which God is the bridegroom or husband to whom his people are wedded. See Jeremiah 3; Hosea 2, Hos 3:1-5, 4; Isa 54:5; Isa 62:4, Isa 62:5. Also, Mat 12:39; 2Co 11:2; Rev 19:7; Rev 21:9.
Will be (βουληθῇ εἶναι)
More correctly, as Rev., would be. Lit., may have been minded to be.
Is the enemy (καθίσταται)
Thereby constitutes himself. Rev., maketh himself. See on Jam 3:6.