They don't explicitly say her age but the mother mentions that she arrived at the isolated house when she was married exactly twenty years before. And Haenel's character had an older sister who died. Therefore, Haenel's character had to be a teenager and in no way did the beautiful actress pass for a teenager. As far as Call Me ( and I loved the book too), before we learned that Armie Hammer had canibalistic interests, he made a most desirable figure, a gorgeous young man. Of course, a horny queer 17-year-old boy (or girl) would have been attracted.