Companion ria keeps attacking me causing all others to attack

Solution 1:

I don't know anything about what caused this, so I can't help you there. However, I do know several possible fixes.

1. Use Calm spell or something similar on them.
2. If you are an Imperial (race), use Voice of the Emperor.
3. If you have the Dragonborn DLC, and have gotten the first 2 words to the Bend Will Shout, use that shout; however, you will have to make sure you hit everybody with it, because otherwise the ones you hit will turn and attack the ones you didn't.
4. This is a LAST RESORT! Restart your game and make sure you do not steal from the Companions, and that you do nothing to make Ria mad!