I just checked dc.fandom.com - they consistently use the pronoun "she" in the articles, but have no origin for her. So either Streaky changed genders in one of the many reboots, or the site editors are misinformed. They say the current version first appeared in 2011.
I ran into that as well when I was doing research but I’m pretty sure the only 2 instances of girl streaky are a Super Sons annual and a story from the Bite-Wing anthology and both of those are like Super-Pets stories and also happen years apart with boy streaking showing up between and after
Whoops, sorry - I misread the year. They agree with your blog, 2017.
OK, I just looked through my PG collection and my Supergirl 2025 collection. Streaky is consistently referred to as "he", "his," "him". Maybe the people at dc.fandom.com don't read those titles? Still no mention of an origin, though.