I'm sure some female was used as the model for Tink's face, but I don't know who.
She looks more like Sandra Dee than MM, to me anyway.
I don’t see the connection between Tinkerbell and MM.
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I think Tink was being compared to Audrey Hepburn
Excerpt:
There is an urban legend that the original animated version of Tinker Bell was modeled after Marilyn Monroe. However, Disney animator Marc Davis's reference was actress Margaret Kerry. He illustrated Tinker Bell as a young, attractive, blonde haired, big blue eyed, white female, with an exaggerated hour-glass figure. She is clad in a short lime-green dress with a rigid trim, and green slippers with white puffs. She is trailed by small amounts of pixie dust when she moves, and this dust can help humans fly if they think happy thoughts.