In Ruby's vlogs, Blakeney doesn't appear at all invested in being on camera. So, I'm not sure she would want start her own channel. If she were going to do that, I feel like she would be actively trying to endear herself to Ruby's audience.
Yeah, Blakeney has no social media presence, has no YouTube channel and seems low-key annoyed when Ruby shoves the camera in her face these days. I don't think becoming an influencer is on her agenda.
Her book was non-profit with all proceeds going to charity, and she didn't publicly advertise it in any major way, so I can't for a second see her friendship with Ruby being based on furthering her writing career. She never goes with Ruby on gifted event trips, and 95% of the gifted stuff Ruby gets doesn't seem like it'd be any use to Blakeney (Miss Patina hand-me-downs don't seem like her style).
I feel like anyone in her life would quickly come to realise that Ruby is a narcissist who doesn't want anyone else to be the centre of attention and befriending her to share the spotlight and further your own career will have incredibly limited success. (See: Molly, whose association with Ruby has served no major, long-term benefit and presumably only damaged her reputation amongst the fanbase she already built.) Even for the videos Blakeney seemed happy to be in, Ruby whittled her presence and anything she had to say away to nothing, because Ruby's gotta be the star.
Which I think highlights one of the many major problems that Ruby will never address: The only time she comes off as remotely relatable on-camera when she's sharing the screen with other people, like Blakeney or her sister, because she visibly reins in her smarter-than-thou robotic renaissance faire reject routine and acts like a vaguely normal human being.
That's a sign that Ruby's probably much less of an unbearable, twirling fuckwit around other people in reality. So Blakeney probably just genuinely liked spending time with her at first and did so less and less the more obsessive and annoying Ruby gets, so now she's just likely biding her time until graduation, takes Ruby's presence in small doses and keeps to herself as much as she can.
Ruby's loaded, so she's probably very reliable with things like rent and bills, and Blakeney, who seems infinitely more independent and outgoing, gets a house to herself for the vast majority of the year and only has to pay half the rent for it.