Have I erred in my reaction to my fiancée's nephew's comment on a picture of a romantic scene with "This is me and you," and my request for her to set boundaries in dealing with him?

The condemnation of the correspondence between the fiancée and her nephew is appropriate, as this speech is reprehensible. The fiancée must fear Allah and adhere to His limits in her dealings with her nephew, and she must not watch or disseminate lewd scenes, nor exchange words about them. We warn that the fiancé is a stranger to his fiancée as long as the marriage contract has not been concluded, and his communication with her should only be when necessary and to the extent of that necessity.