Did She Orgasm?

This is more of a question:

I was at my girlfriend's house the other day. Recently, as in a few days ago, I started to pleasure her with my hand. Well, the last time I did it, I remembered to not only stimulate her hole, but her clitoris too. I was going rather quick while massaging it. After doing this for a few minutes, I felt her exhale hard and twitch all over. Did she orgasm? One of my female friends told me that women have to make noise when they orgasm, but my girlfriend didn't make any noise. If she didn't orgasm, how will I know if she ever does?