Keep in mind that in this case the threat comes from within the groups that agree with her ideology, but believe she is controlled opposition. The same pot of crazy she (unintentionally?) tried to activate.
Really? It's not very believable that someone on the right would phrase a threat like that (i.e. "go away or you'll end up dead, like the last right-wing leader killed by an left-wing environmental activist").
I did some digging and all I could find (in English) was some comments attributing the threats to the "the anti-farmer or anti-BBB lobby" (https://www.dutchnews.nl/news/2022/07/pro-farming-mp-cancels...).
That some parts of her movement became too militant was likely not her intention.
But it did lead to multiple politicians needing permanent security including herself.