She was shaken with all she had undergone in London, poor woman, and this man, who could cringe to her for a large dole out of her pittance, was the beloved of her heart.
He begged of her to put her hand to a bill; a bill which should not become due for six months.

She consented; she was weak enough to set him, as he expressed it, absolutely on his feet.

All debts would be paid at once, and he would never exceed his allowance again; and as to his mother's difficulty, in meeting a bill for six hundred pounds, it was not in Loftus Bertram's nature to trouble himself on this score six months ahead.
That bill, however was the proverbial last straw to Mrs.Bertram.

It haunted her by day and night; she dreamt of it, sleeping, she pondered over it, waking.

Six short months would speedily disappear, and then she would be ruined; she could not meet the bill, exposure and disaster must follow.
Even very honorable people when they get themselves into corners often seek for means of escape which certainly would not occur to them as the most dignified exits if they were, for instance, not in the corner, but in the middle of the room.
Mrs.Bertram was a woman of resources, and she made up her mind what to do.