I'm just wondering what yours guys theory on why Spoil Rich hate blank flank?

4773119 One, She didn't get her cutie mark until late in her life (like nearing adult)

Couple of theories, actually. Or rather, two versions of the same theory.

#1 - Early Cutiemark.
She got hers at a very young age (similar to DT), and was always told by her parents that she was better than the rest,
and believed that this was because of her early cutiemark. Thus, she shuns those who has NOT gotten their marks yet,
because in her eyes, no mark means you're a lesser being, someone without a purpose.
One or both of her parents may also have gotten the cutiemark at a relatively young age, and told by THEIR parents that they were better,
so it may be something that has been passed down throughout the family for generations, and she intended to pass it down to Diamond,
who in turn were to pass it down to HER children, if and when she has any.
However, Diamond went against her mother and broke this trend.

#2 - Late Cutiemark.
She too was a "late bloomer", being a blank flank unusually long (like CMC), and was bullied for it (again, like CMC).
She thus came to the conclusion that Cutiemark = respect and worth, while blank flank = lesser value (same as theory #1.)
So when Diamond got hers early, she made sure Diamond was told she was better than the blank flanks,
and made sure Diamond put herself on top of the rest, always making her believe that she was better than the others,
and especially the blank flanks (including CMC).

4774529
Diamond didn't get hers early though. In Call of the Cutie, she's celebrating her "cute-ceañera", which implies she got it recently. The only blank flanks left in class are Apple Bloom, Twist, Sweetie Belle, and Scootaloo. This suggests she may have been the fifth last in class to get it.

4774538 Hm, true, I forgot that detail.. Thanks for the reminder. (been a while since I saw the early episodes).

In any case, the rest of my theory may still hold up, regarding her mothers mark. :)

And as seen in most CMC-episodes, Diamond DOES seem to hold herself in higher regard than anypony else,
thinking (or at leas tacting as if) she's better than everypony else.

4774545
She kind of is better (in her way) than everypony else. I'm not just talking about inheriting money, but also in knowing how to exploit it.
Pip is a well-meaning but ineffectual leader. One roadblock and he crumbles. That would not have stopped DT, whether or not she had a full piggy bank.

Now maybe DT will use her great powers for good.

4780707 Yeah, I believe she will.
It may not happen over-night though, but she WILL most likely gradually become nicer now,
and learn how to use her influence and parents' money for good things.

Plus, combining Pips well meaning with Diamonds influence, plus the CMC watching over it all,
they can (and might) make some great changes for the better, both in and outside of the school.