Well, I would argue that it wasn’t a fear of commitment as much as unresolved grief. We obviously don’t know her entire back story, but she was married and settled in a house. I think her unresolved grief made her reject the comfort and safety offered by her sister and Dave. Or, perhaps it’s not even sadness — maybe she found a new fulfillment with the people and activities she found to do on the road. I’m more concerned about the people who didn’t choose that life, as she obviously did (or ultimately does).