Bringing in stuff from the manga, will try not to spoil anything
also forgot the name of prez
Ryota, I have no idea, I can see him as a lot of types due to his lack of characterization
I'm not sure how much is portrayed of her in the anime so far, but I think Mary is an INTJ.
In kakegurui twin aka Marys backstory (I could only find one chapter out online ;-; ), we find out that she entered the academy to become the greatest princess or whatnot, and her steps would be this and that to obtain her ideal future,, (possible Ni)
and although it's a bit of a stretch, whenever Yumeko does something "nice", Mary always exclaims to her how much smarter it would've been to do something else instead
What convinces me most is Mary's Fi, throughout the series it's shown that she prides herself on independence and deeply values the feeling of being 'free' from other's commands. This could arguably be Te, but I don't think this desire stems from wanting to control others~
Rather than agreeing with the hierarchy system that seems to be of logical sense to blue-lipstick prez, she claims it to be severely messed up, likely due to her personal morals regarding it.
definitely agree on yumeko-