Yeah. Most of the hats Jiggles wears for alt costumes are rather feminine, plus the Jigglypuff in the anime is generally assumed as female. Occam's Razor and common sense fill in the blanks. Granted, it's impossible to tell for sure unless you're an expert at spotting gender differences (and assume Jigs even HAS those on her model).
Also, I'm really glad to see more F!Robin in Smash pics.