Frank's confession of the engagement to his father was in any way important to Jane. After all, the real power belonged to the Churchills. Frank was practially adpoted by them. The Westons could do nothing for Jane- it was the Churchills who had to consent. Otherwise, Frank may well be cut off from their favor (and hence, inheritance). I doubt Frank wants to give up his comfortable life. Perhaps Mr. and Mrs. Weston would have to make some sacrifices to accommodate Frank's entry to a profession or into his father's business. I doubt Frank had either the perseverance or the inclination for anything approaching real labor (he's not even good at mending broken spectacles and easily distracted even for that simple task).

Jane would have endured better had Frank's behavior been different. All Frank was concerned with was being in the same vicinity as Jane, and have some fun in the here and now. However, all his intrigues and games made it so extremely uncomfortable for a woman in Jane's position, who was really in a very vulnerable state.

Jane clearly could not sit around for two years until Frank worked on his aunt (he does not seem to have even tried). Even if Jane had never met the officious Mrs. Elton, once the Campbells were back from Ireland in a few months time, she would be expected to take up a governessing position.