If she were married she would be able to stifle her love, crush it out, behind those solid, unyielding bars of conventional wedlock.
The fact of Peter's own marriage seemed to her rather dream-like.
There lay the danger.

They had never met until after his wife had left him, so that her impression of him as a married man was necessarily a somewhat vague and shadowy one.
But there would be nothing vague or shadowy about marriage with Trenby! That Nan realised.

And, utterly weary of the persistent struggle in her heart, she felt that it might cut the whole tangle of her life once and for all if she passed through the strait and narrow gate of matrimony into the carefully shepherded fold beyond it.

After all, most women settled down to it in course of time, whether their husbands came up to standard or not.

If they didn't, the majority of wives contrived to put up with the disappointment, and probably she herself would be so fully occupied with the putting up part of the business that she would not have much time in which to remember Peter.
But perhaps, had she known the inner thoughts of those women who have been driven into the "putting up" attitude towards their husbands, she would have realised that memories do not die so easily..