I think that rather than Darcy's infatuation winning because "he cannot find anything in Elizabeth's character to reproach her own," his infatuation wins because it becomes so strong.

His own words support this interpretation -- "In vain have I struggled. It will not do. My feelings will not be repressed."

Given all that Darcy says about his struggle, if he had consulted anyone else about the struggle, I think he would have told her so. He does mention "family obstacles," but nothing about consulting a family member and getting a positive response. Therefore, I think it is unlikely that there was any consultation with Col. F.