Is it true that Satan has the ability to appear among people and marry them, and is there any basis in religion for a mother's rejection of her daughter's suitor on the claim that he is a devil?

Satan takes on forms, but one must be careful that this does not become a means for whispers (waswās), leading the mother to fall into the traps of these thoughts despite her devotion. We do not know what the mother means by Satan toying with her or her description of the suitor as a devil. Justifications for rejection are related to religion and character, not to guessing the unseen. It has not been heard of a suitor being rejected because he is a devil. If people were to follow this, their interests would be disrupted and their lives corrupted. The Sunnah has clarified that the focus of consideration is religion and character. So, if someone whose religion and character you are pleased with comes forward, marry him [to your daughter]; otherwise, there will be tribulation and widespread corruption.