Relieving heartburn is harder to do than preventing it is. So, keep that in mind next time. One way to relieve heartburn naturally is to sleep elevated. You can do this by using a couch cushion or by using four or five pillows instead of one or two. You can also eat some saltines or other dry, salty foods that will settle her stomach. This will soak up the extra stomach acids, a common reason people have heartburn from time to time.
Often, heartburn is caused when stomach acids come up into the esophagus (or the tube that takes your food from your mouth to your stomach). There is no known cure to help the main reason this happens (your valves work like a swing door in this situation, instead of a one way door).