I think you need to elaborate further.
Presumably as her husband, all her assets would pass to you on death, with no IHT payable. If the life policy is written in trust, with you as the beneficiary, I would imagine the lump sum payment would not form part of the estate (although the annual policy payments for 7 years might be added back to the estate if they are deemed not to have been paid out of income).
Just a few thoughts, and not intended as concrete advice.