Board Thread:Episode Discussion/@comment-1599757-20151212162645/@comment-26339753-20151213044555

Phantomlink959 wrote: Ruby sees black and white, and as far as she's concerned Yang is firmly on the light side, she would more than likely be suspicious of the situation as a result. I'm not entirely sure Ruby is as much of an absolutionsit as you make her out to be-I think she's more the idealistic type.

Either way, she clearly saw what happened, and her response gives us all the information we need; she was terrified, positively in shock.