Wow ... okay.  If you choose to perceive things that way, please feel free.  I felt that I have come across in this thread as even keel, non-confrontational and offering the opposite side.  Without belittling or resorting to any sort of "my side is better than yours."

And the point of bringing up the question of "do you have children" was for the only reason of that when you are a parent it can often have a strong influence of what one's stance will be on the topic and gives a better sense of where one's "argument" is coming from.  At no instance was it ever intended as an attack or planned attack.  What would be the point in that?????  This isn't slowtwitch and threads are not resolved by calling someone out as a d-ck or specifically trying to discredit others.  We are usually above that here ....... (although on certain topics I have been known to overstep being polite .... it happens).

Having been a runner since the age of 12 (same age) please, let me offer my $0.2.

Growing up, I was extremely active, and therefore, very small, and lean.  Played soccer, ran around the neighborhood, and then took up cross country/track upon entering junior high (7th grade here in Buffalo Grove).  Junior high was great, and I have the awards, medals, etc. to prove it, I was pretty much the top runner for my junior high in each the 7th and 8th grade.

It was then time to move on to our high school, Buffalo Grove High School, which just so happened to be in the hardest, most competitive conference in the state, and for those of you from this area, that means contending with the likes of Palatine, Wheeling, Barrington and Hersey.  Those 4 were always consistently represented down at the state meets for both Cross Country and Track, all 4 years of my hs career.  Which meant, my team and I just tried that much harder to keep up with those top teams in the conference...not good!

My freshman year, I wanted so badly to still be the "top runner," for our high school, not caring if I was only a freshman or not.  I ran my butt off, no matter what it took, I wanted to be on the Varsity team (which, in the fall of 1992, it was practically unheard of for a freshman female to be on a varsity team).  But I did it, made Varsity, and I believe, to this day, am paying for it now in my 30's.

Earlier in my post I said that I was pretty small/lean, and believe me, I was so "far behind" the other girls, developmentally wise, that the extent of my "overtraining" by my coach, and me wanting to keep up with the other girls on my team and in the conference, helped create the injury I am still fighting today.

Freshman year conference meet, I was hauling azz into the finish (as we all do) and all of a sudden, it felt as though I had been stabbed.  Back then, I was told I had torn my oblique muscle, and while that very well may be the case, after the numerous doctors I have seen, most of them have agreed, that the combination of not getting a lot of time to let that heal, and the over training I did while my body was still maturing, were pretty detrimental in my still having stomach/hip issues today.

I wouldn't wish any of my stress/pain that this injury has cost me on anyone.

That's my story...I have several friends who I still keep in touch with from high school who choose not to run anymore because as they say, "Their body is just shot," so I guess I consider myself a lucky one...while I have days that are "bad" because of this injury, I consider myself lucky that I can still participate, after all these years, in something I love so much!  (And because I think I may finally be on my way to a permenant solution!! Fingers Crossed!)

With that, I am off to the specialist at UIC for a check up!

P.S. For shitz and giggles, here is a pic of me from HS, from the same race I got hurt in, this was about 5 minutes before.

I heard this on NPR yesterday about girls and sports injuries. It refers mostly to soccer and not distance running, but I thought the information about the development of body structure and musculature  was really interesting.

Training May Curb Some Sports Injuries In Women

I'll try to address your specific questions below... 

My brother did a marathon at 9!

I don't believe that 12 is too young for a 1/2.

I also think if you talk to 10 doctors they'll be split down the middle.  Talking to your GP isn't going to give you any answers.

I would search in medical publications for research on trauma caused on prolonged exercise (running) in kids this age.  Might be difficult to find studies though.

Something else to check is the race.  Many races do not allow runners under a certain age to run.  I have seen several half marathons that say youths 14->, but will not permit a younger runner to run.

I have a 12 year old daughter who trains with me.  She has run a 10K (twice) and a 5 mile race, both fairly slow (52:00 for the 5 mile, 1:15-1:20 for the 10K).  I take my daughter out on runs, but generally do not push her on the speed or distance. 

She likes to run, but I think she enjoys being with me more than she likes the running.  If my daughter asked me if she could train for and run a 13.1 mile race, I would tend to let her, but I will not ask her if she would LIKE to run it.  So what I mean by that is, if she asked without me suggesting I would likely not stop her.  However, I would also be very careful how she/we train.  I would also hope, that I would dig deeper into WHY she wants to run that race.  This would help me know that SHE is doing it for her, not to gain something from me.  Competitive parents (even AGers) can tend to give affirmation for things like this that their kids pick up on, they might think one way to gain dad's (mom's) praise is to race well.

So if she is wanting time with Dad, training with him may make sense.  So I would check to see what the motivation is, and make sure she really wants to train/race and not just be with dad.  Something that could be done while riding a bike beside dad while he is running.  (something else I have my sons and daughter do).