The story I read was that before they met she had watched some interview that Alec had wherein he spoke about Salma Hayek and how attractive she was and how intoxicating her accent was to him.

Soon, the light brown or blonde Hillary died her hair dark and managed to begin frequenting a bar that Alec went to. Since she did take Spanish in high school, she made sure to speak audibly in Spanish to someone when she was standing near him. She styled herself (hair, makeup, earrings) to effect a 'Spanish' look. It is very realistic and believable in my opinion.

Once she caught his eye, she was full bore onto the 'Spanish' fantasy that Alec was looking for.

We know that he knew that she was from Boston, but he fell in deep and continued the fantasy to the public, even saying in an interview that 'his wife was from Spain'. Yes, we know her family vacationed in Mallorca a few summers when she was a kid. That does not mean 'her family is from Mallorca'. Good Lord.

And, have you seen the names they gave their children together? Heavily, heavily Spanish. (Romeo Alejandro, Rafael Thomas, Lucia, Eduardo Pau Lucas, Carmen Gabriela & Leonardo.) Their nickname for their brood is 'the Baldwinitos'.

I guess they've both embraced a live 'Method Acting' exercise that they cannot escape from.