I just hv a minute, but late diagnosis is not bad! We didn’t medicate my son until 15 because his grades were good, but this is when I believe non-Add kids really pick up on the differences and are so WORRIED what others think! 
I will write more later but for my son & my experience withh Add meds on myself having ADD & having to increase my meds, now is when the grades really matter for college & meds are necessary! Meds don’t cure the social problem but can help! Read & learn & share with her so she can monitor herself. It is hard though to correct behavior for me but I didn’t realize my problem until I was 50 so my patterns/behaviors are not so easy to change!

I agree with Netty; a late diagnosis is not necessarily a bad thing. She’s probably been learning to deal with it on her own for many years, but here are a couple of resources that might help:

Women, Hormones, and ADD: The severity of ADD/ADHD symptoms will change during the course of a woman’s cycle. Here’s what you need to know to manage them.

Why Girls and Women Go Undiagnosed Doctors who treat women with ADHD have noted correlations between ADHD symptoms and hormonal fluctuations, not only monthly but over the lifetime of a woman.

Thank you, Wendy!

Thank you, both of you—very helpful and reassuring. I am checking out the links as soon as I post this.

I really appreciate your posts.

You’ll see most kids, especially teens have social problems, boys and girls. My 15 y/o son, 10th grade has lost all his friends from middle school. Freshman yr was the worse with bullying, etc.  He is with a boy today after school for the first time in months! All he’s done for 2 yrs is play World of Warcraft! We Just set up a 504 and his grade level counselor said the first 2 yrs of highschool are the worst but towards the end of the 2nd yr things get better socially for our kids becuz the other kids mature too and see the good in them! That was so hopeful to hear today! If you haven’t tried yet, try to see if she likes any sports. Team sports
aren’t the best for adhd kids but some do fine….My
son is in martial arts just recently.  Try youth groups at
church if u go!  Good luck! I know how heartbreaking
it is as a mother!
My 12 y/o is showing signs of add
and friends is starting to be a little more of a problem,
but since I won’t medicate unless his grades take a
dive until high school, I do all the other things I’ve
learned! I want the meds to get them thru the most
important years, HS and college! I hv a feeling I won’t
be on meds forever becuz I keep having to increase
my dose so….just my two cents. Everybody’s body is
different!

My 13 y.o. was also recently diagnosed with ADHD (possibly ODD, dysgraphia and sleep disorder). He is not yet on medication.  I really need help finding ways to deal with school-related issues (forgetting assignments, not handing them in on time, doing them and forgetting to hand them in).  I’m so tired of arguing with him for hours on end just to get him to do an assignment that would have taken him 15 minutes to complete.  Anybody?