User blog comment:Waterwecna/SERIES 5 PROMO PICTURES/@comment-4623180-20120913011542/@comment-5498755-20120913065039

She is Sophie Rundle as Sefa http://merlin-network.livejournal.com/357457.html.

Considering Merlin is in the picture I think we can all assume its Gwens new maid ;p