I joined about 3 months ago and I'm currently in OCS. The Army can make great changes in your life if you want them. If you're a dirtbag, you'll likely remain a dirtbag. I feel that I've gained a lot of discipline that I didn't have before. As part of that, I've gained a lot of will-power and self control. I promise, if you can keep running that 11th, that 12th mile, you will have the willpower to do just about anything. Keep in mind though, basic training isn't like on TV. It's not really very hard, and even total dirtbags make it through.
And while I'm a very open-minded, equality oriented type person, my short 3 months in the Army has shown me what ANY man who's been in as long will tell you: 75% of the women use their sex to work the system, skate on all their work, and get guys to do everything for them. My short time in the military has me almost to the point of saying there shouldn't be women in the military. I know a few very squared away, hard working women, but the rest are just working this situation for all they can.
Basically, if your niece is lazy, or a whore, she shouldn't join the Army, because everyone will resent her and the only way she'll get promoted is by blackmailing people she's slept with. If she's a highly motivated, smart, ambitious person, bring her on, we need more like her.