Estate duty doesn't kick in till over 2 hundred thousand (try tax web site for exact figure).
She has an annual allowance of �3,000 that doesn't go into the 7 year pot, and if she didn't give any large sums any last year she can give �3,000 from last years allowance this year.
So if she dies within 7 years �37,000 or �34, 000 will be added to her savings etc (excluding any left to charity which don't pay inheritance tax). Then the tax man takes 40% of anything over the threshold.
I would agree with Lady Penelope, if you accept this you should be prepared to treat it as a loan, and give it back if she needed it. (If you use it to reduce your mortgage you can increase it again if needed, and save money meanwhile, but if you spend it on an expensive holiday it's gone for ever)