Viridian is startled by Hope, but catches on.
When she and the others are all down in the hold and ready, and if no one seems to be watching, she begins her spell. Within a few seconds the heroes seem to blur and waver like mirages, then meld into the appearances of another pack of motley mercs. They aren't identical to the ones they'd just brutalized up above, but they're obviously inspired by the look of those. Rough men and women with military style clothes and the same types of weapons as the other mercs had.
(Hee...just realized I don't have the Disguise skill! Doh! I have Craft: Artist, if that helps. (^_^) Assuming the power bonus for an illusion disguise is +10, putting it on par with Disguise Self, the total bonus would be +12 for her Cha of 14. Not sure what the rules would say on the subject though.)