What do you mean "continue her Heroine's Journey"? Morgana is the villain! She can't continue something she's not doing in the first place. And no doubt Arthur and Merlin wouldn't take her back after all she's done.

I know this is going to be hard to swallow but Morgana is following the Hero(ine)'s Journey. If the writers end that Journey at this point in S05, she becomes a failed hero because she's taken on many of the characteristics of a villain. Indeed, she is the villain. However, if Morgana continues that journey by gaining a new lease on life say for instance Aithusa breaths life back into her and she changing, Morgana can become a Hero(ine) probably a Modern Hero (the Anti-Hero) or maybe a Neo-Romantic type with a subtype of the Orphan, the Savior, the Caregiver/Healer etc. Don't blame me for it, blame literature because it's part of the Hero Archetype.

I've got some reasons for it outlined here: link but, this gives a more complete version: link

And, while it would be nice for Arthur or Merlin to take her back, they wouldn't have to for her to complete her Journey: Morgana would just need to be involved in returning magic to the land and aiding Arthur and Merlin. Again, don't blame me, it's the Hero Archetype which this show seems to be following with seasons 1 to 4 (though Merlin didn't develop as much as he should but he can catch up in Season 5).

If Season 5 is the final season then this would be the time for the return of Magic to Camelot, Merlin's revelation of his magic to Arthur, and the formation and establishment of Albion (a united 5 kingdoms against a common enemy). If not then some of these events might be delayed, notably the establishment of a stable Albion.

I'm very excited to see Morgana's evolution! She's such a complex character!