ANY liquids that come out of her inner vagina, outer moisture, touching the physical lips or clit can transmit it. It's not the skin itself (unless there's a lesion there!!!) that sheds the virus it is the liquids from the lesions that will prominently carry it, but when there's no lesions she can asymptomatically shed anywhere downstairs!!!! There's less of a chance when she's not flaring up (assuming she is on medications for suppression) to spread it but any liquids coming out of there will always have a risk of spreading. Therefore if only half of the dick fits in there, then you can't be rubbing your parts unprotected by the condom on her open areas that could have liquid on it. Obviously that's more of an idea with the dick thing rather than a doctor proven method lol but the less parts touching each other down there the safer and more kosher it could potentially be