I don’t think it’s unique to being female at all. Maybe more prevalent amongst females? I don’t know.
It’s usually rooted in parent pleasing during childhood. Children have competing needs for authenticity (being true to their feelings) and attachment (being attached to the caregiver for safety/survival).
Attachment needs always trump authenticity, as because of the child’s vulnerability, they risk (or at least perceive that they risk) death through lack of protection. If the parents are scary (eg harsh or abusive) and unattuned (maybe because of their own stress, trauma, grief etc) or unable to regulate emotions the child shuts down feelings to maintain connection with the parents.
When the child hits adulthood, they haven’t learned to be in touch with their feelings, needs, wants, desires, and they carry over the parent-pleasing strategy. But that’s not a good strategy for life and relationships as an adult.
Where is the line between a naturally helpful disposition and an instilled characteristic to please?
I think you’re asking how does empathy develop vs people-pleasing. Children need to go through a naturally narcissistic stage where the world revolves around them and their needs. Then when they’re toddlers they learn to say ‘no’ (defining the difference between them and their parents) - they become their own person from there - assuming the parent accepts that they’re a separate person and allow them to express and develop their boundaries. Empathy develops naturally after that - once you’re in touch with your own needs, you can have a good understanding of others’ needs.
People pleasers get stuck in the narcissistic stage, always looking to please the parents and never developing to learn their own feelings/boundaries. So the healthy kind of empathy never develops.
Look up Gabor Matè and the School of Life on YouTube for some psychology explanations.