Thanks Iggy....
I've found that females which get along from the beginning as mine do, rarely turn on each other even when older. Adding another female into the mix does cause the two "friends" to turn on the new fish, though....
Last time I had female Bettas, there were three in a heavily planted 5.5 gallon. They got along VERY well. Had them for 3years without a nipping incident.... Then, two of them fell ill and died so I added a new female to keep the one left behind company... No dice there, the new girl was killed off in two days. They're odd fish that way.... Knowing all that, I don't have any concerns about Ruby & Opal not getting along later on.
Thanks for the info., though! It's so cool how no two Bettas are alike, no?