I can understand all the other frustrations you list, but in this, the mother is being normal — in my experience, most women want to be pretty (as men want to be handsome), and in death, they want to be pretty as well, that people will remember them as being pretty. This should be seen not as vanity so much as simple femininity (though to most men, “simple femininity” is a contradiction in terms). My own wife of 27 years has made me make the same promise to her. She’s a humble person, not prideful and certainly not vain, but she does want to be remembered as pretty.