I can’t speak for Tulsi Gabbard, but some of the people I used to argue with on Facebook (about Tulsi Gabbard) seemed to think that non-intervention meant pacifism or at the very least a general opposition to war. The kind of non-intervention that Gabbard advocates is a form of passivity, and as you point out, inaction can lead to war as easily as can action.

Pacifism is NOT passivity. It requires that we work very hard to avert war.

Gabbard capitalizes on her military service: she says that she saw the horrors of war first hand and wants to make no Americans have to suffer again (Syrian refugees and Kurds are out of luck, however). As a soldier (she was a medic), Gabbard did I’m sure alleviate the pain of American servicemen, but from the little I know, she did nothing then or since to actively forestall the horrors of war. Just the opposite.

Gabbard isn’t really a pacifist OR a passivist. As Evan Hill points out in the Nation, “The Hawaii congresswoman’s anti-interventionism masks an affinity for authoritarians, nationalists, and Islamophobes.” Propping up the Assad regime and Egypt’s Abdel Fattah el-Sisi, supporting the Islamophobic Indian Prime Minister Narendra Modi, or playing nice with the Trump administration (until recently, when she has become a candidate for the Democratic presidential nomination) have probably done more to increase the violence of war across the globe than to bring about peace and safety.

https://www.thenation.com/article/tulsi-gabbard-president-foreign-islam/