5 The man most wary in her whelming lap.
whelming > submerging, engulfing; ruinous
6 So me, weak wretch, of many weakest one,
weakest > [the weakest]
7 Unweeting, and unware of such mishap,
Unweeting > Unwitting, unsuspecting unware > unaware; unvigilant
8 She brought to mischief through occasion,
She > [Misfortune] mischief > misfortune, disaster; evil occasion > [an] opportunity
9 Where this same wicked villein did me light upon.
Where > [In which, at which] villein > villain; serf