There’s a general misunderstanding of how House committee assignments work. The entire House votes to put each and every member on the particular committees. Though this typically happens via a voice vote (not roll call), it’s done through a normal resolution passed on the floor.

In other words, a committee assignment is not literally decided just by your own party. The whole House must approve it.

To put this in context, Rep. Greene was assigned to her committees via this resolution, which was approved by all Republicans and Democrats. https://www.congress.gov/bill/117th-congress/house-resolution/63/text

In short, the whole House put her on those committees, and the whole House can take her off. That’s how the process works, even if tradition is to defer to the preferences of the member’s party.

(It’s important to reiterate that committee assignments typically happen via a voice vote, which means a lot of individual members may be unaware the vote even happened. But congressional leaders certainly know, and the assignments are always voted on by the whole House.)