I think it would seen really too awkward to say something to her about it later on - at the time, sure, but hey, who thinks that quickly in a situation like that?  Most of us are still trying to sort out what it is we 'should' be doing while the situation is underway.  Personally I wouldn't bring it up later, I'd just say something the next time a situation arose (about the current situation, not the last one, that is!).  But if you feel comfortable bringing it up with her now, then why not?  You are braver than I.  She mightn't feel quite as comfortable with the conversation so I guess you'd have to expect that it may go well, it may not.  We've all got different ways of handling our kids in conflict, but it seems a pretty general understanding that you don't yell at someone else's child! 

Keep in mind that at two years old, group play and sharing aren't something that is typically developmentally possible, despite our best intentions at encouraging it. That is, two-year-olds do not readily understand the concept of sharing, as parallel play is what characterises their interactions (or lack therof!) at this time. Parallel play means children who play next to each other, but not with each other. They may be engaged in similar play next to each other, but aren't really interacting or "sharing". Sharing and group play doesn't usually evolve until children are around three years old, when they start to understand the concept of sharing and interact in cooperative play.