Women are often murdered by a man close to them, whether a boyfriend, a spouse, friend or an ex of some sort. Given the amount and variety of alcohol Maura had purchased, it's possible that she was meeting someone in White Mountains area. If that person was male, he would be a more likely choice for suspect than Bill, who was miles and miles away. If Bill and Maura's relationship was not a healthy one, that might have been a factor in her decision to get some time away from all sorts of pressures. I feel it's likely that someone knows where Maura was going and if she had intentions of meeting some person or persons--and that individual has kept quiet to protect Maura's reputation or to keep a promise she made not to tell.