Is what the writer did by writing novels that include "halal" romance between spouses, and then deleting them after feeling frustrated and realizing their negative impact on readers, correct? And is the idea that these are "ongoing sins" correct? And is her decision to switch to designing novel covers without showing faces correct?

Writing novels that are free from Sharia prohibitions is permissible, and may even be required if they call to goodness. Romance between spouses within what is permissible (such as a husband embracing his wife or holding her hand) is not forbidden. It is advisable to seek fatwas from scholars known for their competence. There is no harm in using photographs on covers unless they are forbidden images (such as nude women). As for hand-drawn images, it is permissible to use them if they are incomplete (headless or limbless) or have an erased face, or if their features are indistinct. It is not permissible to design covers for novels that advocate corrupt beliefs or indecencies. However, novels free from prohibitions may have covers designed for them. If the status of a novel is unknown, designing a cover for it is not forbidden.