I've only read the first few pages but i can't entirely agree with the "if she has the right support". That kind of support is astronomical compared to what 20 year olds + need. For one, (in Canada anyways), you can't legally work until you are 14, you can't drive until you are 16 and only in the daytime. So, how is she supposed to financially support her child and get the child to the hospital if need be. Yes, I know you can get around without driving, but the fact that legally a 13 year old cannot drive is a valid point. Because when she does turn 16 she's a new driver, and with such precious cargo!
All that being said, I suppose, yes, a 13 year old "could" be a good mom, if we look at what a good mom means. That's why I brought up the age of working ability. A good mom should be able to financially support her family. Emotionally, the brains of children are not fully developed until their early 20's. The last thing to develop is the ability to understand consequences. That's why so many teenagers do so many stupid things, drinking and driving, sneaking out, stealing moms car, etc. They are not wired to really extrapolate and think of the consequences of their choices. Put a newborn into the mix and that situation would need massive support!