Zara was the antithesis of the average Nigerian. She was extremely friendly and had been brought up to embrace other people without an air of suspicion. She was open and unpretentious and she had no air of self-importance.
Here you stereotype a set of people. The reader may not like that. It the same thing as saying Black people are dumb or White people are dumb.
Instead you could say "Zara was the antithesis of the girls I was used to" or "Zara was different"
Her befriending me portrayed the friendliness and confidence that I imbibed from that day. Zara helped me understand that no matter where you are, you can always make a connection with someone.
This is a unclear.
As to what topic this should fall under, This is an experience (meeting Zara) and you briefly described its impact on you.
I like the style of the essay.
Reread.If the qualities that you wanted to show the admissions officers are clear, Then a few revisions and you are good to go
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I'm sorry I can't be much help with grammar. Not my forte