The flooding began on Tuesday, following a period of intense rainfall in the region.
Ms O'Loughlin previously said her parents had moved to Spain about 10 years ago as they "always wanted to live in the sunshine".
She said she was told the pair were missing on Thursday, after friends checked on them and found their pets at home.
Her mother, Terry, had told friends they were "popping out" to get some gas, she added.
The couple were both retired and lived in a bungalow with their dogs.
Ms O'Loughlin said she last spoke to her mother the day before the floods, when they "had a good chat," but she was not able to reach either of her parents upon learning of the flooding.
"We talked about mum and dad coming over here next year to spend some time with us and we just ended the call and I'm really glad I said 'I love you' and she said she loves me too," Ms O'Loughlin said.
Emergency workers in Valencia are continuing to search through underground car parks and tunnels in the hope of finding survivors.
There has been anger at a perceived lack of warning and insufficient support from Spanish authorities after the floods.
The king and queen of Spain were pelted with mud and other objects by angry protesters as they walked through the flood-hit town of Paiporta on Sunday.