During the week of Sheva Brachos, a Kalla, without the Chassan, showed up at Shacharis. The question was whether to skip Tachanun. The Gabbai (me) ruled not to skip it, on the ground she was on the other side of the Mechitza and thus in a separate Rishus. Was I right for the right reason, right for the wrong reason, or wrong?
You are correct, tachanun should be said, the reason being not so much the location [rshus] but rather that a woman is not an actual part of what forms tefilla btzibbur [only 10 men].
See Shu”t Shevet Halevi 5:12, 8:24. See also Shu”t Yaskil Avdi [Volume 7, Hashmatos to O:C 3:1].