She’s directly challenging a Sunak invitation here. Between that and the threat to boost her own budget, she’s spearheading a total breakdown in party discipline.
The Tories are very good at rallying around a leader when that person has stability at the top.
But the second a drop of blood hits the water, they're out for themselves. Truss is just doing what all Tories are secretly doing right now, she's just too stupid to do it privately.