Onassis is a competitive show jumper[9] in select events of the Global Champions Tour.

She later chose to compete as a Greek citizen for the Avlona Riding Club in Athens, under the name Athina Onassis.

[18] Onassis began dating Brazilian professional showjumper and two-time Olympic medalist Álvaro de Miranda Neto in March 2003 and moved to São Paulo.

[26][27] The divorce caused complicated legal issues in the courts of Antwerp, Belgium, where Onassis had been living.

[28] Miranda challenged the prenuptial agreement and demanded alimony payments,[2] and there were custody disputes over jointly owned horses.

There have been several estimates of her inheritance, including the island of Skorpios, which was later sold to trusts connected with Ekaterina Rybolovleva,[31][32] with some accounts claiming that Onassis's net worth is less than $1 billion.

[24][11] The trustees Christina selected to manage the estate were Stelio Papadimitriou, Paul Ioannidis, Apostolos Zabelas, and Theodore Gabrielides.

[36] In 1999, a Vaduz court ordered the management of Athina's inheritance to be transferred to the KPMG Fides auditing firm in Lucerne, Switzerland.

In one of her few interviews, published in Oggi, an Italian magazine, she later stated that she blamed "all the problems" on the Onassis name.

Similarly, her stepmother, Gaby Landhage, stated on American television show 20/20 that Athina had told her "if she could burn all the Onassis money, she would do it.