If she is not mentioned then I would assume she is dead - if there was a family row then almost certainly there would be an explicit sixpence legacy to make sure she was disinherited - if she was not mentioned then she could appeal for an inheritance. If she was given a marriage settlement then again I would expect a nominal inheritance (or words to effect that she was already provided for + the customary sixpence). It was also fairly usual for the mother to leave her clothes equally between daughters.

Check wills of grandparents if they were alive after said Elizabeth's birth for any mention - might also be worthwhile checking wills of siblings.