Sentence:  Elizabeth was now most heartily sorry that she had, from the distress of the moment, been led to make Mr. Darcy acquainted with their fears for her sister; for since her marriage would so shortly give the proper termination to the elopement, they might hope to conceal its <WSD>unfavourable</WSD> beginning from all those who were not immediately on the spot. 
Meaning of the word marked with <WSD> tags:  Not auspicious; ill-boding.