O'Donnell, who has long been an outspoken critic of the war and proponent of gun control, posted readers' complaints about the image under the heading "a picture is worth a thousand posts."
"So disappointed to see your little ones with bullets ... where are the guns?" writes one visitor. "I thought for sure you would protect them more from such things ... The internet is NOT OK ... but bullets ARE?? Why? Why??"
Says another: "Wow Ro that photo of Vivi with the bullets made me cry – it's scary to think that there are precious little ones really walking around like that in our world 'for real.' Come on people! Help our babies."
O'Donnell's rep tells PEOPLE of the photo: "Her kids were playing soldier and she took a picture. That's it."
In response to readers' messages, O'Donnell posted a video of Vivi entitled "dress up." The 85-second clip opens with a title, "last year a princess" and shows photos of the little girl in feminine attire as Cyndi Lauper's "Girls Just Want to Have Fun" plays.
After 50 seconds a title appears reading, "this year a soldier." Again, various images of Vivi, this time in the controversial military outfit, appear before a message moves across screen that says "peace out." The closing image is a close up of her daughter's eye.
O'Donnell also addresses the issue in her Ask Ro section. One reader wonders, "Ammunition belts like that aren't sold at toys r us. What would prompt her even [to] want to do that without a little help from you? SAD!" Replies O'Donnell: "buycostumes.com."
Indeed, a search of the site turns up the $6.99 Bandolier Bullet Belt Deluxe, described as "A great accent for your military or cowboy costume!" One caveat: "These are costume accessory bullets intended for decorative purposes only. (These are NOT real.)"
Reporting by MARK DAGOSTINO