I'd say it's more stupidity than blackmail.
"Oh, I saw a video of Ingrid trying to escape form a building, so now I have to do whatever Savannah says and she'll keep her safe".
I mean, come on! How on earth does this make any sense? First of all, the video can be fake (she never saw her alive after she got pierced by that arrow), and even if we accept she's convinced it's real (because a mercenary trying to fuck her is definitely honest and reliable...), she saw her trying to escape, so she doesn't know is she was successful or got captured again. She could have easily gotten killed in the process and if she actually escaped, what makes her so sure that Savannah knows where she is or that she's actually going to protect her after she gets what she wants?
Just a random ass bitch's word is enough to completely ignore her loved ones' sacrifices! And she ends up fucking enjoying it! Because not only we had to watch Savannah "playing" with her, bit we also had to see how her thights got drenched with her cum!
That whole "instant slut" transformation makes no sense to me, other than the dev wanting to shove a sex scene with her in the game. But even then, why the fuck would you want to see sex scenes between the most popular girl and the bad guys, in a game that's not supposed to cater a certain fetish, I don't want to even mention?