With what we know now, it is also possible that Freya is alive. BUT, if she is, she will be totally screwed up. More than likely physically and mentally-- she'll probably be a witch with extended powers due to a forced connection to a supernatural creature (thanks to Dahlia, and also with many "sessions" of Dahlia mentally changing her via magic, just like Esther has done to Elijah...but, by far much, much worse; and teaching her everything she knows) OR a new type supernatural creature (Freya was forced to become this, along with everything else...so after Dahlia broke her mentally...it was extremely easy to make her HATE her family very bad--especially Finn and Esther) that is created when a witch gets enveloped and taken by another supernatural force/entity (more than likely from the Dark Dimension, and it more than likely also happens to be the "beings" that Dahlia is sacrificing, trading, or possible doing something we don't know yet...like "merging" or "body-swapping"; allowing those creatures to come into our realm via extremely powerful and very dark, Black Magic).
If she IS alive, we can only hope that there is a way to break the link between her and Dahlia AND more than likely a supernatural being linked to her (which, if this does happen, we may see these creatures next season). Then find a way to undo the compulsion and mental damage that has/was created by Dahlia--possibly something Davina could pull off...