As a continuing part of a personal project of mine to expand what things I'm comfortable and have experience writing with comes this scenario:
The princess of the kingdom of Rothe has been raised heavily protected from the outside world, for there is a prophecy spoken of her. It is said that the first person to plant a child within the princess would have power over the fate of the kingdom in its entirity, and because of this, since even before she reached puberty, the princess has been forbidden from seeing or interacting with any men except the king. Other women serve her, attend to her needs, all of them, historically, as the princess certainly has had them... But now one of the rival kingdoms has sent a very special woman to sneak into the ranks of her handmaidens, and with her success, they may possibly get exactly what they want, for that woman has the tool she needs to get the princess pregnant, and a ritual to ensure its success. Of course, to make it work she has to make the princess climax before she does, but she's pretty sure she can handle it.
Basic scenario from there: The dick-girl has managed to scedual a "time window" in which the two of them will be alone, and is going to take this chance to complete her goal.