She gave me a left-hand compliment when she said my dress was lovely for something so cheap.
Она сделала мне комплимент с подвохом, сказав, что мое платье прекрасно для такой дешевой вещи.
Definitions
A left-hand compliment (also known as a left-handed compliment or backhanded compliment) is a remark that appears to be a compliment but actually contains an insult or criticism, often delivered in a subtle or indirect way.