Corrector Yui (1999)

Blurb:
How ironic that the fate of the Internet, and the world, should fall on the shoulders of Yui - a technophobe of the first order. When the sentient computer virus, Grosser, infects the global network Com-Net, Yui is transported into cyberspace to combat his evil plans. Only by assembling the eight missing pieces of the corrector program can Yui make the Net safe once more. A dangerous quest, fabulous costumes, a cute sidekick ... Yui’s superhero dreams are about to come true where she least expected it!

Source: www.anisearch.com/manga/3750