Female impotence is a reall thing. Vaginismus. She looks to be suffering from that

OMG THANK YOU I HAD NO IDEA!!!

She's not "impotent" though, just finds penetration uncomfortable. This manga is actually quite sad, in that she thinks being penetrated (which statistically won't lead to orgasm) is the only way to have sex, and by being unable to it dents her esteem so much. I wish her partner spent more time exploring other ways to make her feel good, rather than it basically revolving around him and how she feels so inadequate about not being able to satisfy him in that way