There was like, some bits of small flashback in chapter 1, showing that Tsubasa was abused in the past, once got her hair forcefully cut. This chapter shows what happened after.
If I understood correctly, her dad caught her bringing a boy home and got pissed. She runs away from home, meets Jun, shit happens.
In the present time, whatever the truth for the prostitution question is, seems like Tsubasa felt ticked off/judged, that blondie had bs expectations of her. She means well but, by telling Tsubasa that she 'believes in her' and all, she's pretty much pulling that faith out of her ass, and telling Tsubasa what she wants to hear from her.
Hmm, I kinda get it but I don't know how to explain it lol. Because well, what if she was a prostitute? Will blondie think less of her? Is that how it ends between them, because of a rumour? Something unrelated to their actual relationship? Eh, it's a feeling that I don't know how to put into words
Anyways, I'm betting that Tsubasa lied/isn't a prostitute