Unless your are the US government, you do not have the power to deport anyone.
If you suspect someone of being deportable, you can report your suspicions to U.S. Immigration and Customs Enforcement (ICE). ICE's contact information is at www.ice.gov . Unless you can report specific information, ICE may not act as it gets many reports from disgruntled people.
If the husband is convicted of or plea guilty to a charge of domestic violence against certain household members (including his wife), the government likely has a basis to deport the husband.
Your friend, if she so desires, can review her facts and options with an attorney to protect her legal rights. If she is being physically hurt, she can call the police.
If the abuse rises to the level of a criminal act, you can contact the police when you have witnessed criminal activities and that would start the criminal process that could lead to deportation (removal) possibly based upon domestic violence. There are strict immigration laws againse domestic violence that lead to deportation.