It's mean to embarrass people in public.
Andrea is out to lunch with her friends when she notices Jenna has a period stain on her skirt.
Andrea wants to let Jenna know about the stain.
Andrea pulls Jenna aside and offers her a jacket to cover up the stain.
Andrea tells Jenna that she has a period stain on her skirt in front of the rest of the table.
Jenna is grateful to Andrea and thinks she is a good friend.
Jenna is embarassed and the rest of the group thinks Andrea is rude.