She had pretty much the same reaction as Jimbei way back in chapter 815:
No, there's a huge difference between a "random offhand comment" and "being a part of the Straw Hats". Trying to equate Jinbe's portrayal here to her portrayal in the Zou Arc, where she was sent to the background, is extremely silly.
Nevermind his actual portrayal in Impel Down (there's a reason the theories began here), Marineford, and Fishman Island. And in this arc, where he declared himself as a Straw Hat, with no fear, and left Big Mom's crew. And he's been having synergy with them the entire time!
–- Update From New Post Merge ---
So until the actual moment a character declares that they're joining, they have no chance of joining? I'm pretty sure everyone on this site figured that Franky was joining before Luffy stopped hating his guts.
Franky joining was pretty obvious the moment he got his flashback.