Where is Tina the first wife of Onassis buried?

[Harley]

I think she is buried with her sister Eugenia, but where?

Athina Mary Livanos Onassis Spencer-Churchill Niarchos (19 March 1926 - 10 October 1974) was a daughter of the Greek shipping magnate Stavros Livanos. She was best known as the first wife of Aristotle Onassis.

Known as Tina, she was married three times. Her husbands were:

Aristotle Onassis (28 December 1946-1960); with him she had two children, Alexander Onassis (1948-1973) and Christina Onassis (1950-1988). She divorced him when she discovered her husband having sex in the saloon of her daughter's namesake yacht, the Christina, with the opera singer Maria Callas.
John Spencer-Churchill, Marquess of Blandford (23 October 1961-1971)
Stavros Niarchos (21 October 1971-1974), her sister Eugenia's widower.
While married to Stavros, Tina's son Alexander Onassis died in a plane crash at the age of 24. Tina was devastated by this loss.

Tina Niarchos died in Saint-Moritz, where she was living with her then husband Stavros Niarchos,of a drug overdose. Her only descendant is her namesake granddaughter, Athina Onassis de Miranda.