Whilst the amounts are relatively small, the same complex tax rules apply as they would to a €1m transaction. Goodwill of pharmacies is generally valued at 5 to 7 times EBITDA (i.e. Earnings Before Interest, Tax, Depreciation and Amortisation).
EBITDA needs to be calculated on a "Maintainable" Earnings basis. if your mother was a sole trader and owned the property with no bank debt, and only earned €25,000 a year, then you appear to have overpaid for goodwill! A locum chemist would make a multiple of that.
I suggest that you see an accountant to review all accounts etc. A typical tax advice letter to cover all the angles (from your mother's perspective and your perspective) on such a transaction could run to 3/5 pages etc
Jim Stafford