How do I help minimize interruptions during group meetings as a student? The project I work on has numerous members -- several graduate students, a couple of postdocs, and my advisor. We meet every other week to discuss progress and update one another on our status. Almost to a point these meetings run over, as we continuously find ourselves in tangential discussions.

One effect that I've noticed from these tangents is that certain individuals in the group tend to get interrupted more than others. Specifically, there's a single female postdoc (hereafter referred to as postdoc A) in the group, and it seems to me that she gets interrupted more often than anyone else.

There are multiple guilty parties here -- my advisor, the other postdoc (who is male and is hereafter referred to as postdoc B), even my labmates and I (the other graduate students). We (my labmates and I) have noticed this and are making a strong effort to no longer interrupt postdoc A while she is speaking. My advisor and postdoc B seem to be oblivious to this, and often times will discuss potential ideas and pitfalls about postdoc A's research during her own presentation.

I'm guessing there may be multiple factors at play -- issues of gender, societal norms (postdocs A and B and my advisor are all from different countries outside the US, while my labmates and I are all from the US), power dynamics, etc. And I also realize that I'm a bit biased here -- I work most closely with postdoc A, so I have a sense of loyalty toward her especially. But it's gotten out of hand in my opinion, and I'm not sure as a student how to best assist her.

This post has some suggestions for students and advisors on how to conduct effective group meetings, but it doesn't directly address this issue. I'd appreciate any advice the Academia S.E. community has on how I, as a student, can best support this postdoc during group meetings.
This sort of thing has roots way beyond academia.  There is a lot about the dynamics of women having difficulty being spoken over in meetings (though I imagine it could apply without respect to gender too, based on differing levels of assertiveness).  Maybe a few things to try:


When someone, even your advisor, talks over her, say "Wait, what were you about to say?" addressed to her, so it's not directly confrontational toward the interrupter.  This is as opposed to something like "Wait, let postdoc A finish" addressed to the interrupter, which is more confrontational.  That is, assuming you want to avoid a confrontation with your advisor.
Mention it casually to her after a meeting.  She might appreciate and/or be emboldened by the support.  Something like "What was it you were going to finish saying before soandso took over?"  This way you show you're both interested in what she had to say and also noticed that she was talked over in the meeting.  
Wait until the interrupter finishes, then bring the focus of the meeting back to postdoc A.  "Sorry, what were you about to say earlier?"  or "Hey, postdoc A, what was it you were saying about X a minute ago?"  This is probably the safest thing to try, and if you do it enough the others might even get the point!