It doesn't matter what we think. We can see solutions that a character cannot. What matters is how Erynn perceives the event damaging her sense of self. And in that sense, it is grave. So much so that she lets Ethan control her out of fear.If its also written in a time where such guys were powerfull i would agree...but in this case ...some detail is missing to fully understand her behavior and i aam not really convinced...today every starlet has a sex tape and its not really bad for their popularity...
Would a sex tape damage the life of a person today? Hard to say. I would venture a guess that it would certainly do damage, the extent to which is undeterminable. Would a normal woman (person, male or female) be significantly affected by someone threatening to reveal a sex tape or intimate private details about her life? Hell yes!
Therefore, Erynn's actions are completely normal and acceptable within her character. She worries about what people think about her. What her mom would think if she saw the video and learned that she could not be "strong" against Ethan's threats. What her friends would think of her. Fear is a powerful motivator.