Lost NRB through failed PET

A wants to make a lifetime gift of £325,000 to B.

A is concerned that if she dies soon after the gift to B leaving her estate of £1m to C and D, her nil-rate band is exhausted by the lifetime gift to B.

C and D would suffer IHT at 40% on the full estate as no nil-rate band.

A wants advice on how to protect her estate being prejudiced by the gift to B.

Could B give A’s estate/executors/beneficiaries an indemnity to pay them the loss which would be 40% of £325,000 as taper relief is not engaged.

Would this fall foul of the GROB rules as it is a gift with a condition?

How do other practitioners deal with this scenario which can’t be uncommon, albeit it only arises as B is different to C and D.

7-year term insurance with a sum insured of £130k on the life of the donor written in trust for C and D?

Thanks Paul - that is one option we are considering certainly.