VAWA is when the person is getting the first green card. You say there is already an I-864 - so can't be VAWA, but possibly abused based I-751 (application to remove the conditions on green card). The I-864 is a legal contract between you and the government to keep the immigrant spouse above the 125% poverty line and yes it can be enforced. To protect yourself from any false allegations, you can always write to CIS. Also, you may want to consult with another matrimonial attorney
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I agree with Ms. Vaisman ... you need to talk to an attorney.
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I think your legal issue is more geared toward divorce and matrimonial law and domestic violence, so you might be better advised by a family law attorney. I changed your tags to reflect that.
On the immigration issue, if you signed an I-864 affidavit of support, then she probably already has her green card (but it may be a conditional one). It is legally enforceable. She may file an I-751 to remove the conditions on her green card asking for an exception of the dual filing requirement based on domestic abuse. It sounds like you need a good family law attorney who can help you sort out the financial obligations and the issues of domestic violence. You could write to USCIS explaining your side of the story if you are concerned about her getting her green card without filing with you.
www.gassonlaw.com - Disclaimer: This a general answer to your legal question. Unless you have a signed engagement letter with me, you should not consider this information to be legal advice.