I disagree completely. Did Princess Grace overshadow Prince Raininer? No! She was the consort. In the same way, did Queen Mary overshadow her husband? Caroline is no wife, but she is acting as first lady in many events. She and Princess Stephanie ADD to the event by playing a role as a team in the family unit.
The press and public pay so much attention to what the women wear, their hair style, their jewels, it may seem that she receives more press (or Stephanie or Charlotte). Prince Albert even said in an interview that the interest in his sisters is because they "are beautiful women." If Albert told them for a minute that it was over, they would no longer be at events in that position. They act in those positions at
HIS request. He wants and NEEDS his sisters in those roles because he can't be everywhere at once and it is improper for his girlfriend to act in the place of an official first lady.
HRH (Caroline) has said on a number of occasions that she would LOVE to step aside but that Prince Albert asks her and Princess Stephanie to split the duties as first lady since he is not married. Both want nothing more than for him to marry so that they are out of the spotlight. They work hard to not overshadow him and only take on minimal duties. Heck, they both spend a lot of time outside of Monaco for the exact reason.
Princess Caroline, in my opinion, does not outshine Prince Albert -- he's the Sovereign after all. If you mean that people pay attention to her clothes or jewels, well that's true because women are interested in that sort of thing (in general). However, it's Albert that is in control in Monaco and his press is a bit less "fluffy" or "fashion orientend" and much more newsworthy.
There has always been this is a contingent in Monaco (and I'm not saying you are part, obviously) who puts Caroline and Albert in competition. Both have been interviewed and Caroline herself says that it's bogus. She does not want to be in Albert's position, at all. I think that if Albert marries and has children everyone will realize just how hard it has been for Albert's sisters to assume the roles they have while putting their own interests aside. Once there is a first lady, the Princesses will naturally step aside. Right now, they are simply helping their brother (as they did their father). I think they should be commended for what they've done. I don't envy them at all.