Oh, so sorry to hear you have suffered that. I also have a gluten intolerant friend that uses rice dream consistently. Could you tell me where you found the information about barley in Rice Dream? I take it it is not on the label? I can't tell how long it will take to get better, but you can help your body by getting plenty of water and sleep. Take some down time if you can. Watch out for gluten in everything.
Get well soon,
You'd do a great, great service to your friend by telling him/her about this. Thanks for the good wishes.