Opinions PLEASE

Okay, so let me start off by saying that the nature of this post is NOT about pregnancy.
 I'm 19 years old, 20 at the end of the year. I bought my first car earlier this year, in my name without any help and I make the monthly payments like clockwork. My mom lost her vehicle due to personal choices she made that weren't the smartest. We don't have the greatest relationship and we don't always get along. Today, before the sun rose and before I got any type of "good morning" or even a "hey", she asks me if she could finance a vehicle in my name... I don't always say a lot, but I am extremely observant. I've seen her past and current payment routines on different items, and to be honest it's not very impressive. Lot of late payments, lot of calls from different companies about payments, lot of payment plans on top of payment plans. So, thinking about her history, I'm quite reluctant. I don't wanna say I don't wanna help her but I'm not tumbling over myself to do it. She keeps throwing in my face (and I say it that way because that's exactly how she's doing it) that she helped me when I was younger... but I thought as a parent that wasn't optional. Throwing in my face that she helped her parents. She chose to have me young and then recently to have another child by the same guy, he didn't even want to claim me so he scarcely helped with my upbringing and he's doing the same thing again. She still lives with her mom and of course pays all of her bills and her own. My fiancé and I are planning to get an apartment within the next few months, get married (obviously), and have a child of our own. I won't be living with her anymore, so I don't wanna have to worry about whether or not she's making her payments on time, if at all, if she's gonna be asking for extra money and whatnot. I won't have the money to pay for all of my expenses and hers. The only thing that's mine that's in her name is my car insurance. I work two jobs, go to school, and every now and again I like to travel or just get out of the house, so she desperately needs a car but I don't want to mess up my brand new credit because in this economy that's your wellbeing.