Because they have evidence of her buying some of this: Specific shoes, brass catchers, supplies to build brass catchers and build silencers, bugging equipment and counter surveillance devices, and more. They have her spying on the Rhodens/HG and sharing the layouts of their houses and where they slept. They have her hacking into their devices like Facebook and their phones. They have her on wiretaps ( I assume) participating in revenge conversations against the Sheriff, Attorney General (now Governor) and the main BCI Agent on the case. Angela had bad blood with Hanna and she had the M.M.O. Motive, Means and Opportunity, along with no alibi. Angela was in on all the lies the Wagner's told, she and Jake were the most vocal of the 4 in the media. She was caught in a ton of lies, why lie? Because she was trying to hinder the investigation, cover for her family, Obstruct Justice, and I think to mislead the Agents by pointing them to the Manleys. They have her not only forging custody documents, but she is listed as a guardian. They have her participating and plotting from January through April 2016. She did not have to pull any triggers. She's still guilty of murder. She didn't have to rob the homes but she was part of the whole "sophisticated" plot and facilitated, plotted and schemed. All just my opinion of why Angie would be charged even if she stayed home that night.