You will have to marry her first. Then you can file I-130 visa petition. However, she and her child cannot legally stay here waiting for the visa number to become current, which may take 3-4 years. She must leave the US before her I-94 expires. If she can find other independent way to stay, such as H-1 visa, that will be fine. Overstaying her visa in the US may subject her to removal proceedings. On the other hand, if you later become US citizen, she will be able to adjust her status to permanent resident even she overstayed her visa.
Answered on Jul 13th, 2011 at 1:11 PM