What to do when helping make a minyan for mourners in a shiva house when at prayer time they insist on davening conservative style, men and women sitting together?
My understanding has been that a Mechitza is only required for a minyan Kavuah (a minyan that meets regularly at established times and place)
While we continue to separate at private irregular minyam from custom and perhaps Tzniut, I don't think the lack of separation would prohibit participating in the Tefillah.
In my personal opinion (and you should ask your LOR) once you are there, the reasons to stay outweigh the reason to leave. One should go to great lengths to avoid embarrassing people publicly; I would think particularly mourners.
There are places that count women to make the minyan; that's a different issue.
Aaron's notion of "minyan kavua" sounds familiar; Rabbi Y. H. Henkin has an essay on the topic, if I recall: http://www.amazon.com/Responsa-Contemporary-Jewish-Womens-Issues/dp/0881257826/ref=sr_1_3?ie=UTF8&s=books&qid=1260672749&sr=8-3
- A shiva house is considered "open to the public", so a mechitza is appropriate for prayers there. "But if practically the women don't agree to move to another room, this is considered b'akrai -- a rare occasion -- so prayers shouldn't be prevented because of this."
- An engagement party, sheva brachos or the like is intended for family, not the public, so it is certainly sufficient that the men simply sit together, "so they can concentrate better."
So Rav Moshe certainly allows, if the family insists, to have the men and women in the same room, no mechitza, for davening in a shiva house. He still prefers that they sit separately; I can't tell from the writing whether that would be a deal-breaker.