I think Alfira is an interesting NPC and singer, but I don't see the reason to make her a companion or an adventurer. She's an artist first and foremost who seems pretty dedicated to her craft.
What would be her motivation for adventuring? Being an adventurer isn't for everyone. Not only is it very dangerous, you also have to be capable of violence and killing (which can be pretty traumatic for most civilians). I honestly don't think that fits the character we've met so far. Also remember, 5e adventurer Bards aren't just singers - they are full blown Arcane casters (capable of bending reality at the highest level) that can manifest even more of their deadly magic through artistic expressions.
If you find her an interesting NPCs that you want to know better and would love for more screentime, that's totally fine, a good RPG SHOULD have that, but it doesn't mean they need to be actually adventuring with the party. Think about the NPCs in Witcher 3 (i.e. Dandelion or Priscilla). They might not travel with Geralt, but they get tons of involvement and screen time as civilians. I would love to get more of her and have her story develop like that, but as of now, she really doesn't fit the mold of the companion.
