I don't see this convo heading down the "The 2A should be taken out completely" road, so that's good.
I get a feeling that at some point, though, she may use the "The framers of the Constitution could not have envisioned full-auto weapons" schtick. Advise you counter with "So the 1A only covers movable type, ink, and paper?"
Other than that, so far so good. Keep a light hand with this one.
You may not be able to win her over completely, but you might give her things to honestly think about.