For women, it can equally make sex impossible. Feeling disgusting and that what you're doing is "wrong" removes any way someone can truly be involved in the act. The overwhelming thoughts of "Why am I doing this? I shouldn't be doing this. I don't want to do this," block out everything else and leaves the person lying limp and unresponsive. Any stimuli becomes bad stimuli. Even things that have felt pleasurable previously, are now sources of discomfort and stress. The more intimate, the worse it gets. Oral sex with someone dealing with serious anxiety basically amounts to crying "stop" and physically shoving the other person away. The action is so overwhelming it can cause a gag reflex, crying, and an asthma attack. It's practically painful.
The person feels trapped in the situation and like they can't escape it. It's akin to a feeling of being tied down in a locked room with a stranger. No matter how close or loving or intimate the woman is with their partner, the other person turns into an unknown in her head. The thought process is the other person is causing this fear, therefore, they must be bad. It's an incredibly distorted view of reality that comes from severe anxiety.
As for actual penis entering vagina intercourse, I suppose in a strictly technical sense, it is still possible. In the same way a vagina cannot stopping something from raping it, it cannot just stop, please excuse my poor phrasing here, being "open" due to stress. However, because there would be clearly no positive stimulation at this point, lube would be required to prevent tearing. And even with lubrication, tearing is still likely since the woman's muscles will undoubtedly be "clenching" and causing much friction. She will still be unable to do any movement with the other person and an orgasm in this situation isn't exactly likely.
So, to summarize, yes, a woman is still able to have sex in so far as that something can enter her. However, if doing a tearing, rigid, crying, and panicking woman that doesn't want you to touch her is someone's idea of sex, then that's pretty fucked up.
Anxiety disorders are horrible to go through and they can cripple a person's life. Man or woman. I've always liked this comic as a visual interpretation of what anxiety can feel like. For anyone dealing with such issues, I hope they are able to receive the help they need.
