Your aunt's daughter will have 'legal rights' which (assuming that your aunt has no surviving spouse) means that the daughter will be entitled to receive half of your aunt's 'moveable estate' (which basically means everything except land and buildings). She will have no 'legal rights' in respect of land or buildings.
Your aunt (or her financial advisers) should investigate the possibility of using any large amounts of capital, which she may hold, to buy land (or property) as an investment for her grandchildren. She can then leave the land (or property) to her grandchildren, which they can sell to obtain the money your aunt wishes them to receive.
Chris