Patronising is the existing word to convey the very same meaning without the implicit self-inflicted victimhood women are encouraged to bestow upon themselves.
No, it means something different. Mansplaining is specifically a male person
A. Incorrectly assuming he has greater knowledge or insight than a female person due to the implicit credibility a sexist culture bestows on male people compared to female
And
B. Taking it upon himself to educate said female person when she had not asked for his help or advice, because in a sexist culture a male's desire to impart information to a female person or to have her pay time and attention to something he has decided she should know is more important than her own priorities for her time and attention
There can be no exact general female equivalent to mansplaining in our society because male and female people are not treated with exactly equal credibility (far from it!). Hundreds of years of placing authority and learning only in the hands of men means that the majority of our representations of authority and learning are male, and those cultural biases are the context from which mansplaining arises.
That said, even in this context there are certain limited scenarios where female people are expected to be the authority, generally around children, home and fashion, and in those situations the reverse situation certainly could and does occur. For example, if I, as a childless woman, felt entitled to give a father parenting advice based on my reading or experience of friends' families, that would be a very similar dynamic, and given how well understood and recognised the term "mansplaining" is, I'm pretty sure if I described that as "womansplaining" everyone would understand it.
I do find it interesting that you believe a few decades of popular feminism was enough to "implicit self-inflicted victimhood women are encouraged to bestow upon themselves", but it doesn't seem to have occurred to you that a few millenia of patriarchy might have encouraged men to bestow upon themselves an unwarranted assumption of their own authority. 😜