I have no life until I get my NCLEX results, lol.....so I did some research for you! Lifted this from NCBI / PubMed:
"Body position affects recumbent postprandial reflux.
Katz LC, Just R, Castell DO.
Division of Gastroenterology and Hepatology, Jefferson Medical College, Philadelphia, Pennsylvania.
There is a lack of consensus as to whether there is a difference in the amount of gastroesophageal reflux when lying with the right versus the left side down. In an attempt to answer this question we conducted a two-part study. The first consisted of a questionnaire distributed to 103 gastroenterologists with a special interest in the esophagus. The second was a randomized study in 20 normal subjects given a high-fat meal to induce reflux. Postprandial reflux was monitored by esophageal pH testing for 4 h after random assignment to either the left or right lateral decubitus position (left or right side down) on different days. Of the 87 gastroenterologists responding to our survey, 45 were uncertain as to which position was associated with worse reflux. Among the 42 who did specify, 27 (64%) favored the right lateral decubitus position as associated with more reflux symptoms. The direct comparison of the two positions demonstrated that the total amount of reflux time was significantly (p < 0.05) greater with subjects in the right decubitus position (231 min) than in the left (117 min). Although total episodes of reflux were greater when lying on the right side (227), compared with the left (198), the difference was not significant. In addition, average overall acid clearance was significantly (p < 0.001) prolonged with right side down (0.77 +/- 0.14 min/episode) compared with left side down (0.29 +/- 0.08 min/episode)."
So the upshot is...stay on the left, although if you wound up with the pt on their right, they'll reflux a bit more but statistically it won't matter a whit. Unless, of course, you're the PATIENT, lol....I'd want to be on my left
Edited to add: if your friend's theory was that it would aid digestion to sleep on right side, she's wrong. Your theory wins