Some guys here justify their tool truck loan. Some guys can justify a student loan or paying for school without a loan. Some people can even prove to you with real world math (accountants for example) the difference in their overall compensation for a career with a degree vs without. Education is just another tool you use to do your job, or help you get the job you want.
Yes accounting is a BA degree and yes I stick with what I said that a BS is what most people should look toward for their educational goal. I also did not equate every BA degree is artsy fartsy, just the one example you provided. And no, I did not say it was worthless.
(I am making an assumption here, no offense intended) Let's say something happens with our accountant and he can't be a self-employed CPA now. He could work at a company as an accountant, work at a tax prep company, at a law firm, etc. Without the degree he's a guy who's good at math. With the degree he's qualified for the position. He's the same guy, the paper helps him prove it. ESPECIALLY if you're now looking for a job because your experience may be called into question.
Here is what I would do in her situation. Get the AS degree. Get a job turning wrenches, watch what you have to go into debt for (tools & school both) and continue school until you have the BS. Nights, weekends, seasonally depending on her situation. Will it take time? Yes. Is it immediately going to change her life if she's working as a mechanic? No.
So since the 20 year career was mentioned, let's say she finished HS at 18. 2 years in tech school, she's 20. a few years working & in school, now she's 25 with a degree. Time to immediately quit and get another job? No. Time to tell her employer she wants another position? No. Time to possibly use her free time (no longer in school) to make extra money using the knowledge and/or opportunity the degree proivides? Sure. Time to consider grad school? Sure. Time to take a little break? Sure. Throughout her 20 years as a mech she could choose (or be forced to choose in an unforeseeable situation) another career path.
Let's talk about the other possibility. She goes to work for a garage, shows up every day for 20 years and takes home a check. She gets hurt, she wants extra income for a hobby, she gets tired of doing it and wants to try something else. You going to hire a girl who's got no school and been a mechanic for 20 years for something other than mechanic work? Probably not.
What's the difference? She has options with the degree. And she has more options the more school she completes.