100b. Answer #3: The case is, her engagement was on
condition, and it was not fulfilled.
Isn't it the continuation of rav shmayah's answer?
Yes, it is actually a clarification of Rav Shemaya's answer. On the other hand, it is not exactly what the Gemara thought Rav Shemaya's answer to be, originally, and in that sense it is a new answer. That is, the Gemara is saying that we are not discussing a true "Mema'enes" in the normal sense of the word, but rather a Mekach Ta'os, which can also be called "Mema'enes" in a sense.
You seem to have learned the Gemara correctly.
Be well, and sorry for the delay!