In Hindu tradition, should you consider your elder brother's wife who's younger to you as your sister or as your mother?

E.g., can you prostate before her (i.e., do sāśtāṅga namaskāra) as you would to your parents or elder brother? Does your sister-in-law's age play any role in this?

What do the śāstras say?

Any examples from scriptures in this regard?