Why does the girl not agree to a similar affinity with you? Because you are physically hurting her. But this kind of intima is possible only with pleasant sensations! In the manual: how to properly talk to a girl about such proximity, to prepare her body, to give pleasure. Это и многое другое вы найдете в книге The art of anal sex. 20 techniques and other secrets of caresses (Larsson Veronica)