I never thought that Edward's urgency to leave Barton when he had nowhere in particular to go and no commitments of any kind might have been in order to avoid bumping into Lucy! That could be.

I had been thinking that his staying at Longstaple for only a fortnight, when, again, he had no particular reason to leave at a certain time must have seemed odd to Lucy too. The Dashwoods had no idea he was coming, so he had no real reason he 'had' to leave there. I'd always thought it was because Lucy had pressured him to come, and he allowed two weeks maximum to do his duty and visit his fiance. But, if she started making plans to visit Exeter while he was there, that might be why only two weeks there. She might, indeed, have dug up some connection or other, and it required only the time for a letter to go and come back from Exeter.