Is there a way I can petition her if my mom came to the US illegally?

There is no way for your mother to obtain legal status in the U.S. now. However, as you likely have heard, the Congress is working on a reform of the immigration law. While nobody can say with certainty what the new law will look like, chances are that there will be some relief for parents of U.S. citizens. In expectation of the reform, some immigration attorneys advise their clients to file immigrant petitions for their relatives, even if under the current law these petitions would be of no help. You might want to file an immigrant petition for your mother now - in hope that it will place your mother ahead in the line of all the people for whom petitions will be filed after the reform of the law, or in hope that it will save you some money on the filing fees, or for any other hope. Well, the fees will go up - they always do! The rest of it is pure speculation. No one today - including the President - knows for sure what the immigration law is going to be in a few weeks or months. No one can say for sure whether filing an immigrant petition for your mother today will give you any advantage. Most likely, it would not hurt. So, if you want, go ahead and file it. The Form I-130 and the instructions are available at uscis.gov/forms Follow the instructions, and you should be able to fill out the form and file it. Otherwise, just wait and follow the news: the reform is promised, and should happen soon. We will see what relief, if any, it will bring to your mother and millions of other people.

Your question requires an attorney consultation. It is not a simple question that can be answered on this type of forum. There are many factors that would need to be considered and evaluated. The short answer is that you can petition your mother, however she may have to go through what is known as consular processing. I strongly suggest that you contact an experienced immigration attorney for a face-to-face consultation and give him/her all of the facts surrounding your situation. He/she would then be in a better position to analyze your case, advise you of your options and, if possible, make sure that the necessary paperwork and documentation is presented so as not to delay the process.

You can petition for her but she will not be able to legalize her status within the US under the current immigration laws if she entered the US unlawfully.

You can file petition for your mother and, as a US citizen, that petition is given utmost priority by CIS. If she is now in the US, you can still file her petition as long as she came to this country with a visa, even if it has now expired. You can file the I-130 petition and I-485 [green card] at the same time. She will be interviewed within 6-8 months and if everything is ok, she will get her green card at that time. Realizing that there may be other issues involved in this case and as such, I suggest you hire a lawyer to handle your case. Good Luck

Of course you can petition her. She might also be eligible for the provisional waiver, or, the amnesty that will hopefully soon be law. Either way, I'd consider filing I-130 for her as a start.