Had to have it practically pointed out to her though.
It was obviously a satirical wind up as she now knows just how many TRAs will fall over themselves to attack her. More muppets them for falling for it.
How could anybody not of seen she was being making fun of the TRAs:
'Happy Birthing Parent Day' to 'all whose large gametes were fertilised'
I wonder how long she thought she would have to wait before she could post an obviously prepared response?!
'Devastated and bewildered that my embrace of inclusive language has angered its most enthusiastic devotees, so let's just say: Happy Mother's Day to all females who've raised children.'
I thought it was feminists who were always accused of having ahumour bypass. 
I'm not sure how in terms of her reputation or raising awareness this is, but given the shit that has been thrown at her, this seems quite a mild joke at the expense of gender fluid rainbow unicorn riders!
https://www.dailymail.co.uk/news/article-13180003/jk-rowling-mothers-day-post-sparks-twitter-row.html