If she spent the previous night at home her husband should have seen that she was too drunk to drive, and have been awake when she left and heard the noise coming from the garage. It looks more like she was coming home from a night of drinking--in which case she was probably at a party or at a bar, and others should have been able to report having seen her.
It's all pretty fishy. Did she have a history of excessive drinking? What was her blood alcohol level at the time of her death?
Having just closed that big deal, it’s possible that she did stay out celebrating, but no one has indicated she did. Surely someone else who was “celebrating” knows.