Given the strangeness of the statement, we could try 'The nurse assists her girls due to her stories'. However, this is a very rough attempt at rephrasing something that seems quite muddled in its original form.
Such a question is not suitable. Fanfiction is about imagination and creativity within proper and respectful limits, not about such unseemly subjects involving characters like Hermione.
As it is, this sentence doesn't seem to make proper sense. Maybe you could check if there are any spelling mistakes. If 'cum' was meant to be 'come', then it might mean that your wife invited him to be included in the stories she tells.
It depends on creating a vivid and sensual setting. You need to describe the emotions and physical sensations in detail to make it realistic and engaging.
There are definite ethical problems. Such stories often cross the line of acceptable sexual content. In real - life sexual encounters, any form of sexual activity without clear, active consent is wrong. These types of stories can promote a wrong view of sexual boundaries and disrespect for others' autonomy.