My mom is trying to claim me on her taxes. Is this right or wrong?

I have a question involving taxes and maybe one of you could help me out, I would really appreciate it! My husband and myself filed our taxes last week as a joint married couple. This morning we got a call from H and R Block saying that the IRS could not process our claim because someone else had already claimed me and my tax credit that I get for being a student. Turns out, that person was my mother. She believes she is justified in claiming me because I lived with her for eight months in 2011. My husband and I were married on September 17th 2011, if that helps. The IRS website said that a married person filing jointly cannot be claimed as a dependent, regardless of how long they have lived with their parent. My mom is saying that I have an option to file as a dependent and thus would enable her to get the money that I would be getting, even though she hasn’t and won’t pay anything toward my student loans. She’s also stated that I “stabbed her in the back” because I filed as a married person (but I am!). She says that because she let me live with her while I was a full-time student, that I owe that to her. Her doing this has caused not only our tax returns to be screwed up, but also our FAFSA that we have already filed. So, now I may not get any financial aid for next semester. What can I do?