1 O hateful hellish snake, what Fury first
hellish snake > (Addressing Jealousy) Fury > (In most representations, the Furies' hair is entwined with, or consists of, snakes: see e.g. Aen. 7.342-55)
2 Brought you from baleful House of Proserpine,
baleful > [the] deadly, [the] miserable (perhaps also connoting "hell-fire": cf. 101.16:7) House of Proserpine > (Hell; Proserpine is queen of the underworld, the consort of Pluto)
3 Where in her bosom she you long had nursed,
she > (Presumably, Proserpine rather than the Fury)
4 And fostered up with bitter milk of teen?
teen > grief; woe; pain
5 Foul Jealousy, that turn love divine 6 To joyless dread, and make the loving heart 7 With hateful thoughts to languish and to pine,
pine > waste away