It's true that Diana was an emotionally needy person.
But that, together with Charles fragile ego of having a beautiful young wife pining after him (if not rather clingy), he would have been fine with this. Doesn't camilla call him sir or majesty of something?
Diana, always viewed Charles as her real life Prince Charming. She would have concentrated on him, which would have buoyed Charles fragility. She also would not have stolen the limelight to get public attention as she would have had it at home.
Would he have cheated with lovers and flirtations? Possibly, but she was so enamoured, I believe if he had pledged his devotion to her, these would have been viewed by Diana as fleeting hiccups that mean nothing to him, but satisfaction of his ego as a desirable man, infact, there probably would not have been many because ultimately he had the prize at home.
Camilla took advantage of Diana's young naivety, and weaponised that against her in good time. Very strategic indeed. Diana was never going to remain a child forever - we saw this in how she dealt with issues/charities/people.
What Camilla did was to use her age as 'the mature one' ' who has known you longer and therefore familiar' 'we have so much in common' , in time - thereby blocking Diana be any of these things.
Diana had no space to breath. As far as I'm concerned if Camila had been away for even 5-10yrs, Charles focus would have been on Diana.