I think she had been planning her scape for months and had been stashing cash in a secret account, clothes, etc and whatever else she needed in a safe storage somewhere in readiness for his new life... It is very easy these days to obtain a fake passport and a new identity, change physical appearance... and she could be anywhere in the world trying to get some sense out of his life.
And for that, she needed to start a new life without anyone trying to influence her.
Some husbands may be excessively dominant and manipulative and they would never accept a divorce as a solution. In these cases, the only option is to disappear without leaving a trace. It is sad because of the children, but there is no other option.