Anne and Captain Wentworth were not going to marry until Wentworth had earned enough money to support them and their kids. They were facing a long engagement until Lady Russell talked Anne into breaking it off. Anne would not have been left poor with small children.

This makes Lady Russell's involvement much more problematic to me. She was not intervening about an obvious risk of poverty, she was intervening to save Anne from the stresses of a long engagement. But, as we can see, Anne suffered from the stresses of being separated from her love, and could we believe that it would have been easier on Anne emotionally if Captain Wentworth had died if they weren't engaged?