No, she can’t. She can, however, call for a guy to be her hero, so I guess that’s something.
Thanks to the Huffington Post for publicising Marvel Comics’ views on boys (the t-shirt features male heroes and is listed for boys, though of course it could be worn by a girl) and girls (listed under ‘women’ on the Marvel site and ‘juniors’ or teenage girls on another superhero merchandise site. There is no ‘Be a Hero’ shirt either with female heroes on it or in the girls’ section of the website.
This could be a good pair of images to show some kids you know. Ask them what they think about these t-shirts. For more ideas on helping kids become merchandise-and-media savvy, check out blue milk’s post on the workshop she ran for 5-6 year old kids on sexism.