She's got her memory back and comes back for Bo to help her find some answers that were locked in her memory. That's why Bo is "missing" and Tamsin's with her: that's why EA said it was a valkubus centered episode because they're together the whole episode and away from the others. Kinda like a Brazenwood 2.0. I think that's that also because there is only one pitcure of Bo or Tamsin together in the stills and they're both missing Bo on all of the other pictures.
I hope so! When does each promo usually come out? All the other programs I watch, the promo is on straight after so I never know with LG.
Normally Tuesday afternoon around 4pm, showcase twitter will tweet the youtube link (that's how I watch it). Sometimes it's late...and since today is 12/24, not sure if they will maintain their schedule. Hopefully we get to see Tamsin in the promo...