Later on, looking back

Hi

A woman named Mayfield came to another woman's house (Mrs Baines). Mrs B. didn't like it and started shouting at her.

She stopped (shouting) suddenly, and the angry colour seemed to
fall away from her face; she stared beyond Miss Mayfield
towards the scullery door.MissMayfield turned, expecting
to see either Sydney orWesley (a son and a husband of Mrs Baines) , her mind already fumbling
for some feasible, smooth words that might explain this
angry tirade. There was nobody there, nothing there, until
she dropped her gaze to below the level where a human
being would stand; and there, just in the doorway, was the
cat which was called Vesper in one place and in another,
Smut.

Later on, looking back, she was to say to herself that at
such-and-such a point she knew what she suspected, and
that point, like the horizon to a traveller, seemed to move
onwards with her own advance through time. Actually, she
knew at that moment, but presently dismissed what she
knew as too preposterous for belief.
She felt sick with the kind of sickness which descent in
a badly managed lift can induce. And she knew that what
she suspected must be concealed.
‘My cat,’ she said, in a bright false voice. ‘He follows
me everywhere.’

--- I have a problem with "later on, looking back, she was to say to herself that ...".

Does it mean that some time later (but not now, not in that woman's house) she looked back into the past and wanted to say to herself ...

Or maybe it means that Miss Mayfield turned her head again to look at Mrs Baines (because earlier she turned to look at what Mrs Baines was looking behind her back) and then she thought to herself that she wanted to say to herself ...

I'm not sure how to understand it?