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3 of 6 added 336 characters in body

Jelly, 13 bytes

Œlf“aeiou”L%2

All test cases are at TryItOnline

How?

Œlf“aeiou”L%2 - Main link takes an argument - s
Œl            - lowercase(s)
   “aeiou”    - string of lowercase vowels
  f           - filter - keep only the vowels
          L   - length - the number of vowels
           %2 - modulo 2

Non-competing, 6 bytes (since I just added the function Øc)

fØcL%2

Test cases also at TryItOnline

Same as above, but Øc yields the English vowels, 'AEIOUaeiou'