Does the use of the verb swallow have anything to do with the fish that swallowed Jonah?
Jonah's wife had to "swallow" (accept) the ridiculous story (as an explanation for his disappearance for a few days) that Jonah had been swallowed by a whale and survived.
So "she" is talking about a story that is so ridiculous that not even Jonah's wife ...
In the beginning, Macondo was a city solidly set in reality. Magical things happened, but everybody agreed they happened. However, as time passed by, gradually the hold of Macondo on reality started slipping. Things became increasingly illusory. There are several instances of this:
Fernanda's prolonged correspondence with the imaginary doctors.
The massacre ...