Thanks a lot for your answer. So, if I'm not wrong, the steps to follow are...
1- Marry her in her home country
2- File form I-130 on her behalf at the US Embassy in her country.
3- Come back to the US and file form I-797 and form I-129F
4- She applies for a K-3 visa at the US Embassy in her country and if the K-3 visa is approved she can enter the US.
Is that correct? How long does all the process until she can enter the country take?
Another question... Am I legally married in the US if I marry her in her country?
Thanks.