You have put up some really good and well thought out points.
The whole Arhaan Rashmi showmance was obviously planned. They wanted to portray a friends-turned-lovers story, but that whole idea went off with Arhaan's eviction. Then with Arhaan going to every damm media outlet and talking about proposing her, and he was called back to the show.
Personally, I think the BB makers wanted to show a big proposal and engagement (if not marriage) between Arhaan Rashmi in the show. But as a pair, they garnered 0 interest. However, at this time stories about Arhaan being a fraud also came up. So instead of the marriage engagement route, they went with the fraud boyfriend route. I still do not think that Rashmi knew about him having a kid, and she kinda feels indebted to him about how he got her through hard times. Arhaan spoke about Rashmi 's financial condition in extremely bad taste with Shefali. ( I think he did that to appear to be a somewhat 'mahaan' person, after the last week's WKK). However, he also narrated the incident to Rashmi in a different fashion. Coming to Rashmi, she is not the brightest bulb in the box. From whatever I have seen her in the show, she has been gullible, easily-influenced and too trusting. She also has major image-consciousness issues. I think, her being little too nonchalant about this whole matter is because she does not want to make a further mockery of her life on the show ( a show which she only accepted because of a probable fraud she loved), and also because somewhere done the line she still trusts Arhaan (I have seen people be weirder in love).
Overall, I do not think this would end up in marriage. Especially after her damm family member came and told her to think about her decision. I can be waaaaay off the plot, and all of this can be a sham, and I may have to join the #ArtiArmy when they get married in the show. 😆
Anyhow, I started liking Rashmi in the show before Arhaan was in the picture. And have kept liking her with or without this presence (mostly without). This girl has a lot of faults, but she also has some great moments. Her good moments never had anything to do with Arhaan .And I have kinda developed a soft spot her 😆 So yeah, till she makes a maha popat of me by getting married on the show , I will be rooting for her.