I'm replying to this before reading any of the other posts, so take it for whatever it's worth:
No! No! No! And....oh yeah, Hell No!
Nevermind that your parents moved back to Taiwan, and didn't take their underaged child with them, leaving one young daughter to raise said minor. This is a great responsibility that now falls to you. Tough love and all.
The first and foremost thing you now need to do is get your sister some personal financial, credit, investment education.NOT, AU her on your (I'm assuming) hard-earned credit. Making her AU won't educate her. You'll just get the bills after the fact, and of course, you dare not pay any and all of her charges. Even without the card, she can use the numbers online, etc. As you well know, this is an age where she will be under intense peer pressure to "keep up with the Jones", flashing their own AU cards. Not cool to put her in that position without benefit of your credit expereince.
Instead, get her a kiddie checking and savings account. Lots of banks have them for high school students. You may have to be primary owner, but the second, the minute, the moement she turns 18, get your name off of it and make her primary. Trust me, I know whereof I speak.
Next have the banker who opens the account give her "the talk". Encourage her (the banker) not to pull any punches; rather than "selling the bank", give her the hard cold facts of monehy life. You know the drill. NSFcharges, statement dates, Chex Systems, ATM charges and money bank fees...
Show her how to set up a "spending plan", not just a budget and savings plan. Many an adult got into trouble because they were taught to save every birthday cash gift, but never taught how to plan for day-to-day expenditures, and short/long-term expenses, or big-ticket items.
Now, if she doesn't have one already, encourage her to find a way to earn part-time money to fund her accounts...babysitting, dog walking, McD's, crafts, whatever. Each month you sit down with her and go over how to balance, how to check her statements for suscpicious activity and how to dispute if necessary.
Teach her not to spend everything in her account to within an inch of its life. Good practice for a future credit card holder.
You'll get to be hands-on with ushering her into the world of credit and money, without the potential "burn" to your FICO and credit files. She'll get to show you you MAY be able to handle being an AU responsibly if you still choose to do that. But, remember, just making her AU on your credit cards teaches her zilch. You still get the bill, while she gets to spend. And, also you can always add her as AU to your cards the day she graduates from college and gets her first full-time job and it'll look the same as if you added her today.
FYI, most kids aren't thinking any further about what AU means than, "I get a shiny new credit card with my name on it that I can use for daily spending, CASH ADVANCES FROM THE ATM...(yee GODS!!!) and emergencies....like that ski trip my new college buddies are going on that weekend and, well I've got a credit card, and I'm sure my big sister would want me to fit in, and take a break from my studies." While you're thinking, "she'll pay for 3 science books and some school supplies and will promptly send me the money for it before my statement even cuts!" Ha!
I did see several post saying, "sure, it'll help her for when she gets her own cards, etc." Even if you AU her 30 years from now, if will still report on her card as if she was AU from the first day you got the card!!! That's the point of AAOA.
Don't help your lil sis con herself out of her future. And don't mess yours over on a 17 year old guilt-tripping you. Grow up...both of you.
Church out.
