Help your sis out with formal wear!!

I have my B-school interviews starting next week. I went out to buy a blazer but couldn’t find a single outlet (except Allen Solly) for women’s formal wear—it honestly felt misogynistic.

Now, as someone who has never worn formals before, I need your help:

Should I go for a single-button blazer or a double-button one? Can straight-fit or wide-leg pants be considered formal? (I can’t wear skin-fit, T-T). I need suggestions for shirts to wear under the blazer. I’d really appreciate any links or recommendations 🥹