You will be subject to capital gains tax at 20% on the increase in value in the shares from the date you acquired them to today's market value.
Your mother will receive a taxable gift of €7,000 (the €10k less the €3k small gift exemption) but if the value of this gift does not bring her total gifts from children/siblings/aunts & uncles since December 1999 to over €49,000 there will be no gift tax payable. If gift tax is payable, she can reduce this by the amount of CGT you pay, but must keep the shares for two years.