Jesus didn't get baptized until he was 30.
The WTS cautions people from getting married too young, or too quickly. Baptism is supposed to be even more serious than marriage, so it should not be rushed, and shouldn't be undertaken too young, because of peer pressure, or because the congregation or her dad thinks it's time. Think of some people she might know who got baptized young, and then got in trouble and ended up DFd. Nobody goes into baptism with the intention of eventually being DFd, but circumstances change, and you don't want her to have regrets.
Baptism is merely an "outward display" of a personal dedication to god. Just like a wedding is an "outward display" of a couple's intention to spend their lives together. She probably knows that there are people who shouldn't be married, or ended up divorced or separated, and sometimes a few of those divorced couples can still be friends. But that's not an option with baptism when you're a JW. You want her to keep her options open.
She's got lots of time to decide on baptism, but she needs to focus on her education first. Finish high school. Go to college or university. Start a career and have marketable skills. Show her some career options and pay expectations. Show her what it costs to rent an apartment, buy a house, feed a family, what her clothes and make-up costs, how much a vehicle and its maintenance costs. Jehovah ain't payin' for all that... she will have to, and she won't be able to afford nice things if she's Pioneering™ or has to take minimum wage employment to support herself. Show that she will want a good job with benefits and a pension plan so she won't have to work like a dog until she dies.
The WTS shoots itself in the foot by discouraging education of its young people. When I finished high school in the very early 80s, I was pressured into getting baptized - Armageddon™ was Just Around the Corner™ back then too. It's been over 30 years since I got Baptized™, and now I wish I had trusted my gut and waited. I can't have a relationship with my JW siblings [I'm not DFd or DAd BTW, they just think I'm Bad Association™] or my nieces and nephews by them. My kids aren't allowed to associate with their cousins [nobody among them is Baptized™, but again, my kids are Bad Association™]. My never Baptized™ siblings have a relationship with the JW ones... and they do way worse $h!t than I ever did. It's just so unfair and messed up and ridiculous, but that's what my life turned out like, just because I changed my mind and decided I couldn't - in good conscience - be a practicing, believing JW anymore.
