Charcoal, 21 bytes

⭆Ｓ⎇№aeiouι§⁺↥ιιＬ⊞Ｏυιι

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 Ｓ                      Input string
⭆                       Map over characters and join
   №                    Count of
         ι              Current character
    aeiou               In literal string `aeiou`
  ⎇                     If exists then
             ι          Current character
            ↥           UppercaeUppercase
           ⁺            Plus
              ι         Current character
          §             Indexed by
                   ι    Current character
                ⊞Ｏ      Pushed to
                  υ     Predefined empty list
               Ｌ        Length after push
                    ι   Otherwise current character
                        Implicitly print