Faye needs Bubbles.
Why does Bubbles need Faye?
Purpose. And believing she's worth something. It's not discussed but Bubbles has a lot of size self confidence issues. Faye is her first real emotional connection and someone who makes her feel she's worth something which... Because of corpse witch she remembers that at one point she was treated like she was worth something... she was used to eliminate those people.... But she doesn't remember what it feels like.
I remember what it was like to be loved thoroughly and fully when I was very very young. The permanent tragedtht followed that love does not change that memory of being loved or it's power.
Bubbles doesn't have that. She can guess that she had and knows she had companionship with crewmates but she has no memory of real compassion for her.
And even if she did... Fayes feelings for her would be still very new. In the current context it a kind of feeling she is reaching out for most desperately with the added realisation that it is even more powerful than that which she has lost.
It's deep. I have one or two things in my life where I have the memories but not the emotion and even if I'm glad of it there is still this feeling of profound loss. If we are to assume standard software concepts.... Bubbles has lost that emotional resonance and with the way she talks it is like she has had none at all.
It makes her a tragic figure which is why her finding Faye and Faye being open to what she feels is so important.
Sadly, it's that exploration of women's love for women that is rarely seen and even if I'm reading a lot based on my own experiences it's kind of impressive to see it coming from a cis straight bloke.
It's why comics are a brilliant medium. Batwoman, Bombshells, and this comic as well as Big Finish's audioplay ATA Girl explore women romance 20 times better than even the most critically acclaimed telly and film.