Mmm, this is interesting because I think growth in Blake BL fic gets painted in a few specific shades. The dominant one is probably trauma recovery—seeing Blake navigate the aftermath of Beacon, the White Fang, his family legacy, all while building a trusting relationship. It's less about becoming stronger in a fight and more about learning to be vulnerable. You see a lot of fics where he's the one who's always been the protector, and the growth arc is him accepting care, sometimes from someone like Sun or even Jaune.
Another big theme is redefining strength. Canon Blake ran away a lot, so fanfiction often explores her staying and fighting in a different way: fighting for a relationship, for a found family. It's not just political activism but emotional resilience. The growth is in her communication, overcoming her flight instinct with a partner who grounds her.
I also see a lot of 'unlearning' narratives. Unlearning the isolation instilled by the White Fang, unlearning prejudices about humans or even other Faunus, through the lens of a close romantic bond. The partner character often acts as a mirror, challenging her assumptions. It's slower, more internal growth compared to the big battle sequences in the show.
Endings in these stories rarely have her fully 'fixed,' which I like. The growth is shown as ongoing, a conscious choice she makes with her partner's support.