Rebbe,
The Gemara on daf 43 makes a distinction between a woman who remarries without waiting the three months and one who does. If she was simply a meureses we can allow her to stay married and to proceed with nisuin after the three month waiting period. If she had done nissuin she shouldn't stay with him but should get divorced. The presumption is that she had no relations with the second husband in a state of areusin.
Didn't we learn elsewhere (kesuvos?) that in Yehudah chassanim would have relations with their kallah in a state of erusin. Would you say that our Gemara wouldn't apply in Yehudah?
B'kavod,
Sam Kosofsky
Dear Sam,
Hello there and thanks for mentioning this interesting point. As in Kesuvos, a woman in Yehudah who had Yichud with her future husband as was the local custom is treated as a woman who already had relations with him. I assume that this ruling applies to all issues which apply to Nisu'in.
Kol tuv
Y. Landy