What was her crime? She is a Russian spy, who was reporting to Moscow and operating on their orders. She has spent years (since 2015) trying to establish relationships with Republican politicians -- with the aim of using those relationships to accomplish the objectives of the Russian government.
She got her "in" with those Republican politicians by becoming an active participant in the National Rifle Association (NRA). After becoming close th NRA leaders, she used that to introduce herself to conservative Republican politicians. She and her mentor, Alexander Torshin, funneled money through the NRA to help Republicans (especially Donald Trump).
Her indictment didn't name the Republican politicians she was dealing with, but that will be disclosed when she comes to trial. It turns out that those politicians were played by the redheaded spy -- and whether they knew it or not, were colluding with Russia.
I think we're just seeing the tip of this iceberg, and the future will reveal a lot more to the embarrassment of the Republican Party. The photo below shows NRA leader Wayne LaPierre with Butina.