Best place to invest life insurance payout

My father passed away in February and my mother received a large life insurance payout. She has two children on disability and one who will always be a dependent. What are some strategies she can take to make sure that money is invested/growing? She does not have an active job, so can not place any into workplace retirement accounts. She receives a consistent pension payout each month, has the mortgage paid off and also gets social security, so most of the life insurance is currently sitting in a high yield savings account.