What is the ruling on a suitor calling the fiancée's mother to check on them and inquire about their well-being, and does the ruling differ if the fiancée's father has passed away or if her mother is joking?

If the legitimate marriage contract has not been concluded, then the fiancée's mother is a stranger (non-mahram (definition)) to the suitor. It is not permissible for him to speak with her except to the extent that is permissible with a stranger. It is permissible to inquire about her well-being if there is no softness in speech and no fear of temptation, while limiting it to what is necessary and avoiding jesting if she is young. However, if the contract has been concluded, then the woman's mother becomes a mahram to her daughter's husband.