I think... we should consider it as a last resort. Knowing what happened to the natives when the Null attempted to destroy the parasites the first time...

[As vehemently as Marian wants to see the parasites stopped... she's also not keen on the idea of dying if there's still any other possibilities left. But at least someone else has the idea in mind now, if something should happen to her one way or another... ...or if the parasites follow through on their 'investigation' plans in some way.]