Batiks aren't 'printed', they're immersion dyed. The design results from the wax resist (called that because it resists the dye) applied to one side. The side that had the wax on it could probably be called the 'right' side, but the only difference is that sometimes the design edges appear sharper/cleaner on that side.
For most quilts (including Tropical Nights
), you can just use whatever side you like best for any particular block and not worry about whether you've flipped some over ot not. Tell your sister (politely and with a smile) that it's your quilt, so your rules.