It isn't 'caring about religion' the matters, but, having reached the age of responsbility, what does one do with Jesus Christ. 'Devout' this or that won't get anyone to heaven; only a relationship with Jesus Christ can do that.
As to 12 and 13-year old girls, only God knows whether they had reached that point and, more importantly, what they did with the offer of Christ. But, if they were not of responsible age, they are covered as innocents before Christ and go to heaven as any infant or young child would.
Our responsibility to exercise our free will to accept Chrisit arises, obviously, when we are mature enough to have one.