Being vegan or vegetarian is not about being morally perfect, it is about doing the bare minimum to not be responsible for the torture and death of millions of individuals. It's not perfect, it's just the first step.

I doubt the carnivorous plant will even be in someone's plate, but whether that's ok for vegetarians to eat it or not is beyond the point in my opinion.

Eating an animal like a cow kills WAY more plants than I could ever eat in a day, so you see, it's about choosing to minimise exploitation and torture of other beings' bodies.