Is there anything that he can do she has been here for almost a month and my brother has not seen her after petitioning her?

Whom are you trying to help in this situation? You want her to have the green card or not to have it?

This sounds like a case of marriage fraud if she married for the sole purpose of getting a green card. If so, your brother could report her to the USCIS and they would investigate whether fraud was committed. If so, she could be deported, and if that happens, your brother's financial support obligations will end. But this would be a long process, especially if there is more to this story (sometimes women leave their husbands when they feel that they are being abused by them, for example). If she plainly took advantage of your brother and he was nothing but kind to her, he could report this incident as a marriage fraud.

Part of the requirements for Legal Permanent Resident card is that there is a real marriage, from what I understand based on the facts given is that your brother petitioned for his spouse and that at some point the true intentions of the party became known to your brother. If the beneficiary has not received their LPR card he could definitely call USCIS and let them know of the situation and withdraw his application. The beneficiary would receive a conditional legal permanent resident card which must have the condition removed two years after. Part of removing the conditions is to prove again that it was in fact a bonafide marriage. I would have your brother contact USCIS and let them know that he wishes to withdraw the petition.