Subtleties of what is implied, not just said. It implies Ling Qi has a low opinion of herself, but is aware of it and wants to be better. It implies she considers these traits defining aspects of her. It implies she's willing to be scarily honest to a White cultivator.
There is a claim here that the statement "I am a greedy selfish girl" implies 4 things. 1 of which it is arguable that it is implied, 1 of which the statement does not imply, and the last 2 which it might imply. But let's be honest with ourselves here, that is not the only thing that the statement implies and the other implications are damaging to us. So let's not cherry pick which implications we want to imply.
"I am a greedy selfish girl"
The first thing the statement implies is that we only joined Cai for the material advantage. That we joined for selfish reasons and greed. That we don't care about the ideals espoused by Cai only what Cai can give us.
The second thing the statement implies is that we want to better ourselves. An implication can't be drawn that we want to be better people, because we haven't made a statement about wanting to change, but the implication that we want to raise up in the world is there.
And really, that is the only things that can be said to be implied from the statement itself. Then there are the implications of saying the statement.
The first implication of the statement being said is that we have guts of brass. We have the courage to say the statement (with the implications of the said statement) to a person who is capable of crushing us or making our life difficult without too much effort.
The second implication of the statement being said is that we are incredibly stupid. This is a person who can make our life extremely difficult and we want to throw out all niceties? To engage with her at the most basic primal level without dealing with any of the trappings of nuance? We don't know how she would react, and we want to delve to this level already?
The third implication of the statement being said is that we aren't scared of any possible retribution. Implying that we only are allies of her daughter because of resources might be dangerous, we don't know, but saying it as bluntly as this implies that we don't care if it is dangerous, or that the penalty for possibly offending her is well within our ability to handle.
The fourth implication is that we will be brutally honest with the Duchess, for good or ill.
The fifth implication is that we are incapable of softening brutal truths when under pressure. Not a particularly good implication to make when we will be dealing with politics.
I mean, let's not try and pretend that money was the only reason we joined Cai. It wasn't. There have been plenty of good reasons outside of money that has been listed, and simply communicating that we did it for the money is not fully expressing the reasons and pigeonholing us in the eyes of the most powerful person in the entire province. There are much better ways to communicate the material reasons as well as the plethora of other reasons.