>>121016399>>121016338*sigh*
The cops. Episode 4. They were COMPLETELY mind-wiped of all knowledge of Westview. Monica and Jimmy even acknowledge that the effect is more widespread than just the borders of the Hex, but it had no effect on them.
Monica enters the hex, is partially controlled, but shows signs of recognizing a problem (having to come up with a name on the spot as well as Agatha's suspicion).
Then, she is able to shake off some of the control on her own and reference Ultron. Wanda throws her out after realizing she can't be fully controlled.
Darcy warned Monica about repeated exposure to the Hex, and Monica herself wanted to take precautions to prevent any sort of mind control or reality warping. The truck was their attempt at blocking out the different types of radiation. The truck failing to get through without being re-written reveals to us that the hex is more than just radiation, it's magic.
So Monica knows a few things at this point:
>She can resist the hex mind control to some extent>Her body's molecules have already been permanently re-written>Wanda is suffering>Hayward is dangerousSo she decides to risk being re-mind controlled to save Westview, hoping that whatever allowed her to resist the first time can work again. She gets through, and it works even better than she thought, unaware that she has already gained her powers as Spectrum/Photon.
If you didn't catch all this on your first watch you're just slow, and that's okay.