If your significant other comes from another culture, the only way to truly get to know the person is to understand the subtleties of her language and culture. If her heritage is Portuguese or Brazilian, consider saying "I love you" in the language of Bossa Nova. Impress her by learning to write and say the phrase in Portuguese.
Write the phrase "Eu Te Amo." Of course, knowing how to spell it isn't enough -- you need to know how to say it too.
Pronounce "Eu" as "Eiu." "Te" is pronounced like the "chee" in cheese. Even though the words starts with a "T," you do not make a "T" sound when you say it. That is just one of the many quirks of the Portuguese language.
Sound out "Amo." It is a combination of "ahh" (like the beginning of the word Amish) and "Moe" (like the bartender in "The Simpsons"). Put the emphasis on the "ahh" part of the word.
Put it all together now: Eiu chee AHH-moe.