We're 139 as well, but all g's and o's. We'll see how things go... My daughter is quiet in school, a bit of an introvert and also a bit of a perfectionist. Not sure if she'll stand out as her class has lots of really outspoken, bright kids. But my Dd is very much a well- rounded student, which is what I hear the committee is looking for.
I don't think they care about well-roundedness in the traditional sense all that much, frankly. It's not like a college admissions process. They are looking for kids who exhibit a level of academic giftedness such that their needs are not going to be met in the base school program. So if, by well-roundedness you mean having lots of outside interests, I believe those are relevant only to the extent they demonstrate the characteristics of a gifted child, e.g., an intense, sustained interest in a particular subject & wanting to learn everything possible about it, or other things of that nature. But the fact that a child plays soccer & basketball & tennis and is on swim team and plays the clarinet and is a girl scout really has nothing to do with the eligibility determinations. (Let's face it, every kid around here is signed up for a zillion activities.) And in fact, they changed the name of the program from Gifted & Talented to AAP because people thought that if their kids were gifted at baseball or piano or whatever, they should be in the program. So the change reflects that it's advanced academics and that's the type of giftedness they're looking for.
Now, if I totally misunderstood you and by "well-rounded student" you meant she does well across all subjects and all aspects of school, then yes, that's very helpful to her chances.
Having rambled on about all of that, it sounds to me like your DD is pretty likely to get in, based on the high NNAT and report card. I wouldn't worry about for now it if I were you - I think you are in good shape! (And I am envious of that score - I honestly don't believe my 96th percentile kid belongs in the base program, but because we're below the cutoff, I'm already anxious about the screening process next year!)