TBH if Deadpool killed her it would at least be better than the movie's Villain Sue portrayal of her as someone who can beat everyone without breaking a sweat.
One of the many things the movie got wrong about Wanda is exaggerating her power level to the point that no one can beat her, when in the comics she's always been someone who has to use her powers creatively to beat people who are more powerful than she.
It's kind of impressive how it got her so wrong in so many different ways.