From the storytelling perspective, I'd say Taunt might be the only viable option since everyone will want to strike her down :-D Flank not really, because you don't want any of your units near her. Corrosive could be, or burn - spreading the plague to your own team, but under a different name.
For gameplay, taunt and flank make the most sense.
RE: Ulfga is here, coming in few hours! Is it balanced?