She (as the claimant) would have to prove that the food caused her "long-term negative effects" and the shop (as the defendant) was negligent in knowingly offering spoilt food - a legal concept known as "causation" that Wikipedia describes as concering:
the legal tests of remoteness, causation and foreseeability in the tort of negligence. It is also relevant for English criminal law and English contract law.
The claimant must prove that the breach of the duty of care caused actionable damage. The test for these purposes is a balance between proximity and remoteness:
that there was a factual link between what the defendant did or failed to do, and the loss and damage sustained by the claimant, and
that it was reasonably foreseeable at the relevant time that this behaviour would cause loss and damage of that type.
I cannot find any relevant caselaw using the given circumstances of far-future ill-effects, but it seems unlikely (to me) that such a claim would succeed on the information available due to the remoteness between events.