You don't trust Ruby by any means. She may have been there for Sam after Deans death, but there was something off. When Dean came back he didn't trust her either. However he was more vocal about it then you. You kept your mouth shut in order to avoid conflict.
That was until you found out about the demon blood. Dean of course went off on Sam, while you went to confront Ruby. You sure as Hell weren't going to let her get off that easy.
"What's your plan? I know you're not just doing this to help Sam. You're only out for yourself."
"Wow, that hurt. Almost as much as Lilith sending me away!"