I'm not sure I understand your question, but I will explain the sequence in the Gemara and hopefully that will answer your question.

The Gemara writes that at the time of Sakanah, the Takanah of Yom Revi'i was suspended. The Gemara wants to know what was the time of Sakanah, during which it must have been dangerous to get married on Yom Revi'i. The Gemara suggests that there was a Gezeirah that whoever got married on Yom Revi'i must have initial relations with the Hegmon. The postulate was that this is a Sakanah, for the Torah requires a person to allow himself or herself to be killed rather than commit adultery. To this the Gemara counters that since the act would be only adultery b'Ones, there is no Sakanah, for in a case of Ones a woman is not required to give up her life in order to avoid sinning. To this the Gemara answers that in any event the Tzenu'os would allow themselves to be killed and not sin, even b'Ones.

D. Zupnik