In Chapter 45 we read the following passage: Not a syllable had ever reached her (Miss Bingley) of Miss Darcy's meditated elopement. To no creature had it been revealed, where secresy was possible, except to Elizabeth; and from all Bingley's connexions her brother was particularly anxious to conceal it, from that very wish which Elizabeth had long ago attributed to him, of their becoming hereafter her own. He had certainly formed such a plan, and without meaning that it should effect his endeavour to separate him from Miss Bennet, it is probable that it might add something to his lively concern for the welfare of his friend.
Two concerns here: First, couldn't Georgiana have aimed somewhat higher in marriage? I'm thinking of both greater fortune as well as rank. I realize Darcy’s first concern would be for her happiness and it is a credit to Bingley that Darcy would hope for such a union. Still, it seems to me that it's an unequal match, both in terms of position in society and fortune.
Second, JA writes that it is probable that Darcy's vehement opposition to a marriage between Jane and Bingley must have at least a little bit to do with his hopes for Georgiana. Do you think this is something Darcy acknowledges to himself? He mentioned nothing of it in the letter to Elizabeth, but that doesn't mean he didn't realize it in his own conscience. Even if that were his chief motive in separating Jane and Bingley, he could hardly have spoken to Elizabeth about a subject so delicate as his hopes for a husband for Georgiana. But if he did recognize his own feelings in this matter, wouldn't that have made his actions seem selfish and underhanded? I'd hate to think of Darcy in that way. Quick, someone say something that will allow me to believe that Darcy's hopes for Georgiana had nothing to do with his actions in separating Bingley from Jane. Quickly! Or I shall be obliged to think ill of somebody!