The role of a new Fringe Agent has been filled by Aussie actress Georgina Haig.
As per Seriable:
She’ll play Etta, a new Fringe Agent who shows up in this season’s Akiva Goldsman-directed 19th episode.
Etta is the partner of Henry Ian Cusick’s male agent. Whether they’ll be over here or over there agents remains to be seen — the info on that front has been a bit contradictory, perhaps intentionally so.
Haig’s character has more long-term potential that Cusick’s seemingly one-episode based gig, so it will be interesting to see how and where she factors into the overarching story; possibly depending on that fifth season.