You only need to say "no, thank you".... Now we got another dummy school arc
Seems like in this high society that's actually incredibly rude (basically being given a golden opportunity that anyone would normally never get) saying no to something is just not really the way. Being seen as rude or ungrateful by outright saying no, even nicely, would probably ruin her goodwill through the years.
It sucks but you need to do what she did, saying no but in a way that doesnt seem like you want to say no,...its just it backfired because of the situation with her mom and her mom's friend. Otherwise it probably would have worked normally.