It's scary how good she is in this whole kingmaking business. No woner she could elevated his brother who is a bastard son into a legit king in previous live. Putting the Grand Duke into the throne would probably easier for her.
This jewel thing, not only she got to dismantle his opponent source of income, she would probably gained leverage of the Marchioness who hold the jewel. Never mind that she managed to cast favorable light into the Grand Duke in both the common peoole and probably in moderate nobilities too. 3 strokes with just one move (and those are the ones I could see from this chapter alone)