Eva Sweeney, 3, who was on holiday from Scotland with her family for the celebration plunged 20ft from a balcony at the Ostan Hotel in Goath Dobhair.
The toddler crashed onto a roof before falling onto the concrete below.
Medics had to revive the tot after she crashed on to a roof, then slammed on to concrete.
Amazingly, she only sustained bruising to her head and body, two black eyes and an injured shoulder.
However, Eva had to spend five nights in hospital while undergoing checks.
She was admitted to Letterkenny General for one night before being transferred to Temple Street Children’s Hospital, in Dublin.
Health and safety bosses are investigating the incident last Saturday.
Eva’s parents Sarah and Joe, both 35, of Kings Park, Glasgow, are preparing to sue the owners of the Irish hotel where the drama happened.
It is understood the balcony’s railing has now been boarded up.
Last night, Eva’s dad Joe said: “It was frightening. Eva’s an amazing wee girl, she’s lucky to be alive.”
Her uncle Simon Murphy, 34, added: “It’s a miracle that Eva is still with us.
“I was told on Sunday morning and booked a flight to Ireland straight away.
“The paramedics had to revive Eva at one point, so we feel really lucky that she’s still alive.
“I saw her sitting up in the hospital with two black eyes but she was still smiling.
“The wedding party went on to the hotel balcony and there was a band playing. It appears that Eva was playing tig with some other children when she put her hand out to lean on the balcony fence – but fell through it because the plastic panelling was missing.
“We’re lucky there was a roof below because it broke her fall.”
A spokesman for the Health and Safety Authority said: “We’ve been made aware of the incident and are conducting an investigation.
One of the hotel’s owners, Charles Boyle, said: “We have spoken to a member of the family and we understand the girl is now, thankfully, well and out of hospital.”