Yep, I totally get where you're coming from and don't think you should feel obliged to do anything you don't want to or don't think is necessary based on the opinion of one person. If your DD is happy and thriving that's the main thing, there can definitely be a downside to diagnosis.
You may find that as hormones change through the teenage years, that situation also changes though so do be prepared for that.
Just knowing neurodivergence is part of who you are can also be helpful. On a personal level I was diagnosed with ADHD just over a year ago at 49. Obviously no one knew what it was when I was growing up, much less than it affected girls. I've not gone down the medication route as I have a physical issue that means I can't take stimulants and the other medication options are too faffy for me to contemplate.
What the diagnosis has done is explain to me why I've never felt I really fitted in, and that the way I've done things throughout my entire life has been different/wrong. I don't try to force myself to do things the 'right' (neurotypical) way anymore which has been really liberating!
I've also realised, through the course I'm studying as well as my work, that there were so many indicators for me throughout my childhood and teenage years that either went unnoticed, or I was too scared to tell people about (I now know I had raging OCD from the age of about 8, for instance).
I absolutely wouldn't suggest rushing down the diagnostic path, but do be aware that things change and your daughter may be doing a better job of masking than your realise.
Communication is the best thing and making any decisions about diagnosis together, if and when you are both comfortable to do so. You can also get pre-diagnosis counselling to help you both make the decision if that's the tight thing for your DD.