She was way too emotionally distressed to even think about doing thing like revenge sex. Once it got to the morning after, at that point Sakura really had no choice in how she acted from here, there was only one road forward, and then blonde showed up. As for the forced part its a huge gray area where Sakura was initially hesitant but gave in because there's no way she could physically even stop the fuckboi at that point imo, fuckboi worked quick and also Sakura has a history of getting foggy headed pretty easily at times like this.
That's what I meant; she was sad and distressed, even though she already knew about Fuckboy's romantic interest. Aside from her roommates, she had no friends, so Fuckboy was the closest thing she had to one. From the start, Sakura had shown that she lost control during sex, and on top of that, the fact that she knew Fuckboy loved her, that he was handsome, and that she thought he was a good person—all of that combined made it difficult for her to stop him, even if she tried. By the time Sakura reacted to hearing Shinobu's call, she was already in bed, without underwear and with her legs spread, and before she could react, she was being penetrated. After chapter 128, many said she had been raped, although some changed their minds in chapter 129. The truth is, it's documented that some women can experience pleasure during rape, even if they obviously don't want to be raped.