If your mother gives you more than $15,000 in one year she will have to file a gift tax return, Form 709, as macuser_22 said. She will not actually have to pay any gift tax unless all the gifts she has given in her lifetime are more than $11.5 million, but she will have to file the gift tax return. If your mother's total assets are anywhere near $5 million she should consult a tax professional before making any large gifts.
Your mother might need professional help to file the gift tax return. TurboTax cannot be used to file a gift tax return.
