Why would she stay with a person like that? Because, sadly, a lot of people stay with abusers for YEARS. I am not a psychiatrist, but I do know that when a person experiences abuse (what was her childhood like?), their brain and body tells them that even though it is sometimes bad, this person is there and they cling to that. Maybe things will change? Maybe it's because I did XYZ? Maybe....
Anyway, to the case. This is bizarre. I also thought well, she doesn't seem to have her head together and thought it had to be suicide. But then suddenly there is her ex putting gas in her car at 1:20AM, running by Walmart at 8AM, and getting a car wash? And in one interview, a neighbor said she didn't normally park like that? This all sounds a little off. If you have a sick kiddo at home, what the heck are you all doing out at 1:20am getting gas? And if people believe she was meeting another man (or whatever the thought is), you think the other man would be A-OK with her ex-husband filling up her car? Her ex-husband wouldn't be filling her car up if there was another man around. Nope. And NOW I'm thrown that she commented on her live journal at 3am on the 27th? The writing style looks like hers, but if somebody knew her really well they might be able to duplicate that.
I'm very confused. But I don't think she went off to take her life or disappear willingly. Something is wrong here.