If you can give her a long notice period, then 1 week of severance is more than reasonable.
If you can't give her any notice, she should get 2 weeks of severance to make up for the standard notice period.
The "1 week per year" thing is called severance, but it's really more like a bonus for lengthy service. In your case, you are talking about real severance, that is to be used to help her transition to another job.
Don't forget that she will also be eligible for unemployment, which will also help her during the time she is looking.