For starters, it wouldn't be referred to as martial law. But, no matter what it's called, it would probably be modeled after what we're seeing in Italy and Spain, which is much less draconian than China's approach to contain COVID-19.
Ultimately, the right to life transcends human rights.
If we do reach the point of lockdown, it probably wouldn't go into effect immediately, so people can relocate. In practice, it might start with a curfew and then lockdown might go into effect at midnight on such and such date.
But, the reason for her question was, what if she ends up at home, alone? The thought of that was making her feel at bit vulnerable. That led to a conversation about the 2nd Amendment. Most foreigners are puzzled by America's love of guns and she feels that, since "everyone" has them, it puts her at a disadvantage.