Yeah, she would feel so betrayed but I just wanna point out the difference between Kei and Chihiro's action tho.
Like for Kei it's more like self destructive action since he was in Entertainment industry, so it easily got power dynamic there, like so many many real life idols who got to get physical payment for their position. Even tho he consent for them to use his body, it still not an actual consent tho. In his case, it's more sad than Chihiro's. The mc would feel bad that he did that behind her but at the same time feel pity for him.
I mean in Chihiro route, she knew the obvious cheating but still wanna be with him and said she dgaf about it. like GIRL