Lauren Cosgrove, 8, from Barrhead, met the mythical creature, alias Linden Wolbert, 32, from Los Angeles, thanks to the Sunshine Children's Charity.
Mum Laura Paterson, 35, left, said: "Lauren has been obsessed with mermaids since she was really young. She ran straight to the edge of the water and couldn't stop smiling. Seeing her face today when she saw the mermaid was magical."
The little girl was was born at 27 weeks and spent the first year of her life in hospital. She has had to live with several serious health complications as a result.