(This is conjectural - made-up)
The Pink Lady Code.
Rule 1: Obey the Pink Lady Pledge: Act cool, look cool, be cool. Til' death do us part, think Pink!
Rule 2: At no time is a Pink Lady to become romantically involved with a non-T-Bird member. Restriction is rescinded only after graduation from school or expulsion. A Pink Lady will not date a: Jock, nerd, Preppie, anybody non-cool, or member of a rival school or gang. T-Birds, not Nerds!
Rule 3: The Pink Lady jacket symbolizes that the wearer is the girlfriend / consort of a T-Bird member. Upon leaving the Pink Ladies under duress (violation of rules 1 and 2, expulsion, illness, death, school transfer) or personal choice, wearer must return the jacket to the T-Birds to avoid damaging said T-Birds' reputations. `They got a Rep to protect'. Rep is everything.
Rule 4: A Pink Lady must present herself in appropriate attire at school at all times - Pink Lady jacket a must! Flashy, seductive costumes are not allowed, as they allow non-T-Bird students (and other males, staff included) to see what is for T-Bird eyes only. Seductive attire appropriate only to be worn at functions if accompanied by their T-Bird escort / boyfriend.
Rule 5: A Pink Lady is to have a cigarette and matches / lighter on her at all times, for herself - cigarette equals `cool' - plus her fellow Pink Ladies and T-Birds (and favored Rydell staff) who might perchance wish to bum a smoke.
Rule 6: No Pink Lady is allowed to interfere with other Pink Lady to T-Bird relationships. If the leader of the T-Birds is spoken for, unattached Pink Lady is not permitted to trespass on fellow Pink Lady relationship. If the leader of the T-Birds is available (Pink Lady girlfriend leaves - see rule #3), unattached Pink Lady may make advances on unclaimed T-Bird leader. See rule #4, apply it. The prettier the Pink Lady, the more interested the unattached T-Bird will be.
Rule 7: Returning to Rule #2, Fraternization outside of T-Birds, if all members of the T-Birds are accounted for - have Pink Lady girlfriends - unattached Pink Lady must remain single. Addendum: If unattached Pink Lady has interest in non-T-Bird student, and wishes to pursue relationship with said student, see rule #3.
Rule 8. Contrary to popular belief, (see Rydell school year 1958-1959 (Grease), Premarital `coupling' (Sliding into home base - thank you, Louis DiMucci) isn't a requirement for being a Pink Lady. Just don't die a virgin or die wearing your mother's underwear.
Rule 9: If you're a non-romantic friend of the Pink Ladies, you're a friend for life. Friendship (non-fraternizational) may include nerd/brainiac (good for assistance with essays), and jock. NOT allowed: Gossip Girls (Patty Simcox), or annoying cheerleaders (Stacie & Gracie).
ADDITIONAL - Added June 16, 1962 If unattached Pink Lady meets and falls for former-nerd-turned-badass-biker, who saved the butts of T-Birds and Rydell students, fraternization rules rescinded!! (Co-signed by Johnny, Goose, Louis, Davey, Steph, Sharon, Paulette, Rhonda, Dolores).