You can certainly add in an extra row so that you place the buttonhole on a RS row. (Actually, with 13 rows between buttonholes, you should be back to a RS row anyway.) Just remember to keep to the 6 row pattern repeat.
It depends on the next pattern directions. It may not be critical which row of the pattern you're on. It may be more important to be be ready to work with the RS facing you (so that the next row is an odd number row).