Not too sure but if she is within her rights.
Effectively, this could mean that you own the old chairs which you should remove, if only to pi$$ her off. Ask to see the receipt for the originals. If the receipt shows that the chair is say, 10 years old, then I'd offer her €40 due to depreciation, ask her to sign a receipt written by you and move on. Chances are, she doesn't have the receipt. If she doesn't, ask her to specify the make/model and shop where it was purchased.