Firstly - we are all different and sometimes that is just how we are, however i understand your worries and why you ar e concerned.
Im a teacher & mum and agree with the "mollycoddling" thing - it is so hard when they are little to not do everything for them but by doing some things for themselves they gain vital life skills.
I think from my own experiences the best way for a child to develop confidence is through self-satisfaction & personal achievement. I dont think being told verbally always works (how many times have others told you that you look great but all you see is the opposite??)
This doesnt need to be a big thing at your DD age, just little tasks that help to develop her independence. Things like choosing own clothes & dressing herself, making you both lunch (im not suggesting 3 course meal - sandwich would do! lol), climbing up the older kids frame in the park/jumping down. Bringing in the biscuits when you have guests in the house ,sorry - thats all i can think of right now!
Also the role play & karate are good as they will give DD a sense of control and a method of coping & dealing with difficult situations (even though i doubt she would ever Karate kick someone, just knowing that she can can be enough)- and therefore making her more confident in social situations.
However, i dont see anything wrong with what you are doing so far and I am sure as DD matures and grows so to will her confidence and at the very least, her coping strategies.
I can reccommend "Raising girls" by sharron biddulph, easy to dip into & easy to read
if you are still wanting to read up.