Yesterday her mother Candelas Moreton said she was hopeful the romance had a future.
'They are both single. My daughter is young and very pretty and there is obviously nothing to stop the things that happen between two single people from happening between them,' she said.
Last year Miss Sastre broke off her engagement to Belgian businessman Michel de Maleingreau d'Hembise.
Montgomerie's agent Guy Kinnings said: 'Colin has got nothing to hide - he and Ines are close.
'But at the moment he is just concentrating on the golf tournament.'
Montgomerie himself was just as discreet, saying only: 'We are good friends and we have been out to dinner.'