This is a no if it were my real sister.
And seeing as how I've gotten so close to my roommate, who wants to get into the hobby - I can see us working with a client together - but not doing a "doubles" job like I've done with doubles partners previously. (see recent review with Reese or previous ones with Autumn Spring, who the later, we have seriously gone all out in all kinds of ways)
I have to see my roommate face to face, everyday, for all kinds of things. Share a bathroom, go to the store, live life, hang out....we are best friends. I don't know if I would want to be going down on her and her going down on me - as we aren't attracted to each other that way in real life. And in the hobby, I like doing things genuinely.
I can see us taking turns sucking cock and kissing each other. (I've totally made out with her before - it's just below the belt that would be a no for us)
She is very interested in doing what I do, and is interested in the idea of coming along to an appointment with me. So I think the idea that was posted by the IP is interesting. I just think of her more like I would a sister. Although I might not heavily make out with my real sister.
(her boobs aren't as big as my roommates either)