The .45 is a better home-defense round than a 9mm which has over-penetration properties. Although I’m not familiar with the gun she bought, the .45 is what I would have recommended. A .40 may also have been a good choice.
You think a 45 won’t penetrate sheetrock? Neither a 9mm or 45 is likely to go thru a human with a lot of power left over, and either will go a long ways with a miss..