How and when should my wife light candles when the only orthodox minyan in town davens maariv and recites kiddush during mincha gedola?

Shalom, Thank you for getting back to me with the details. First of all it is strange that the orthodox shule is accepting Shabbat and davening Maariv so early in a way that is forbidden. Do you have a Rabbi there? If so, perhaps you should speak to him about it (-in a very respectful way, of course). Perhaps because of the nature of the community and the extreme times you have there he relies on an opinion we are not aware of, or calculates the daily times according to a different, or minority, opinion. However, if, for whatever reason, the community really accepts Shabbat before plag ha'mincha, their acceptance is not an acceptance at all. I do not agree that "at least they take in shabbos (successfully) exactly at plag by their very conduct of shabbos seuda". It is not clear to me at all that people sitting in their individual houses, continuing to eat their meals can be considered as a communal acceptance of Shabbat that would obligate you and your wife. Firstly, they are not acting as a community (such as when a community prays together), but as individuals. Secondly, their act of eating is forbidden, as they should be lighting shabbat candles, praying maariv, making kiddush etc, all of which they did before plag hamincha and are invalid. Can a forbidden act be considered as a communal Shabbat acceptance? I doubt it. Thirdly, see the responsa of Rav Fienstein zt"l, (Igrot Moshe, O.H vol 3, 38 - at the end) where he raises the doubt about whether a community that accepts early Shabbat just in order to eat early, and other conveniences, obligates everyone to accept Shabbat with them. This is certainly the case in your community, and so even if they all really accepted Shabbat in shule at exactly plag hamincha, it is not certain at all that this would obligate your wife. You should, therefore, wait at home until plag ha'mincha, and then let your wife light candles and accept Shabbat with that lighting. You should then accept Shabbat (through saying Kabalat Shabbat) then pray maariv. After this enjoy your Shabbat meal with Kiddush. Blessings - Da'vid Sperling.