It would be treason to let her go.

It would be cruelty to her.

He was bound to reflect that she was of tender age, and the foolishness
of the wretch was excusable to extreme youth.

We toss away a flower that we are tired of smelling and do not wish to
carry. But the rose--young woman--is not cast off with impunity. A
fiend in shape of man is always behind us to appropriate her. He that
touches that rejected thing is larcenous. Willoughby had been sensible
of it in the person of Laetitia: and by all the more that Clara's
charms exceeded the faded creature's, he felt it now. Ten thousand
Furies thickened about him at a thought of her lying by the road-side
without his having crushed all bloom and odour out of her which might
tempt even the curiosity of the fiend, man.

On the other hand, supposing her to be there untouched, universally
declined by the sniffling, sagacious dog-fiend, a miserable spinster
for years, he could conceive notions of his remorse. A soft remorse may
be adopted as an agreeable sensation within view of the wasted penitent
whom we have struck a trifle too hard. Seeing her penitent, he
certainly would be willing to surround her with little offices of
compromising kindness. It would depend on her age. Supposing her still
youngish, there might be captivating passages between them, as thus, in
a style not unfamiliar:

"And was it my fault, my poor girl? Am I to blame, that you have passed
a lonely, unloved youth?"