...we can't expect even Elizabeth to be prudent *all* the time. ;-) Remember that it takes a warning from her aunt to really make her stop short and consider the situation in a strictly prudential light, although of course she knew the facts of life before. I think up to this point she has just been going along, enjoying Wickham's company and attention, not thinking too much about the future. Remember that Mrs. Gardiner has to remind Elizabeth not to have Wickham invited to Longbourn too often, which was a less than prudent thing to do. As for the ball, remember that Elizabeth was in high spirits at the time, and I think the phrase "capturing his heart" may be a bit of a lighthearted exaggeration.