Answer: The correct answer is: "I'm one of the coolest females you'll ever come across."
Explanation:
Logically, when we say “one of,” it must be followed by the noun in plural form.
Since you are referring to one in a group. You cannot refer to “one” if there’s only one female. You refer to one female in a group of females.
If you leave out the "one of" and just say "I'm the coolest female you'll ever come across." That would be correct as well.
Hope it helps! :)
