Bananagirl was the cousin of Bananaman and was introduced as a new pupil in my Super School strip which began in the Beano back in 2008. Bananagirl was the idea of then-editor Alan Digby, and Ian McCloughlin wrote the script. (Iain wrote most of the Super School stories.) She never appeared in a "civilian" identity and seemed to be Bananagirl permanently in order too fit in with the theme of the strip being about superhero kids learning the ropes. She had similar powers to her cousin, being able to fly and some super strength, although she seemed to be smarter than Bananaman.
Super School ended in 2011 and haven't been seen since, nor has Bananagirl. Will she ever return? No idea, but Beano characters often turn up when you least expect them, even decades later (in the case of Big Eggo!) so maybe one day...!
By the way, I've never drawn Bananaman for a comic but I did do a sketch of him last year at a very breezy Comics Salopia last summer in Shrewsbury. Neil Kenny videoed it for the Blast Process YouTube page. Click on the link to see it...