The people who founded this country disagree, which is why they included this specific freedom in the very-limited list of rights that are guaranteed at the federal level. In the wake of last year's riots, most of us now recognize why they did so: you cannot rely on a government to protect your family from criminals if it becomes compromised or corrupt. If she doesn't like the way the country is structured in its founding documents, she is free to move someplace that is more in keeping with her preferences.
Or maybe her focus would better be spent on considering the shooter, his mental issues, and the current culture of hate-based identity politics wherein victimhood is used to justify violence against those who differ from you. The gun didn't decide to kill anyone. The man did. If he didn't have that particular gun, he'd have had another... or an improvised bomb... or poison... Remember there were a million people hacked to death by machetes in Rwanda.