Akash and Arshi have shared a real bond for some time now. Still remember an akhada scene when nobody had whisteled for Arshi except Akash. Arshi too seems to be a true friend with a golden heart and genuinely cares for Akash. Notice in todays's epi she looked upset when Luv kicked down his picture.
She misses Akash and tried to make peace with him several time with "chai chahiye" "Tu bata maine kiya kya hai" etc. i have no doubt shes a yaaro ka yaar types person who truly grieves loss of a true friend. Its not just about the game for her.
BUT on Akashs side its something different. Yes in part hes miffed that Arshi picked Shilpa over him. But thats because having spend good amount of time with both Vikas and Shilpa (and playing a self confessed role in softening their feelings towards each other) and observing them both in close quarters its obvious to her that none of this was planned. And Akash is wrong to accuse Shilpa (her ma)
The biggest reason though that Akash has disassociated with Arshi is Hiten. I have a feeling Akash wants to form a Jodi (romantically) with Arshi. Which is why he suddenly wants her to stop talking/flirting with Hiten. He's not REALLY romantically attracted to her, but after the Face Wash task he thinks Bigg Boss has dropped hints, and that they will go far if they become a real jodi.
He has taunted her about going after only married men. But Arshi jaan feels safer in harmless flirting with Hiten (she is completely clear that he has a wife and is a loyal husband, but feels safe as being a gentleman he wont really say anything TOO demeaning to her) notice Hiten has never disrespected Arshi as much as the other male/female contestants. The most he calls her in fun is naagin. Although HE has the license to legitimately talk a lot of shit but he refrains. Salman too has hinted that the flirting looks cute and not cheap. So Arshis right why stop a good thing.
Whatevers going on in his head Akash needs to figure it out who his real friends are fast. Before he does/says more hurtful things, which might bring such a sweet bond to a point of no return.
P.S. I dont think Akash is playing double agent anymore like he confessed to Shilpa in the bathroom. As hes mean to them even in private.