About the title "カノジョも彼女" While they do read the same, the fact that they use Katakana and Kanji means that they're conceptually different. Originally, the word "Kanojo" can mean both "she" and "girlfriend" no matter how it's written (be it Katakana, Hiragana, Kanji or Romaji), but in this context, seeing that they use two different way to spell, it's safe to assume that you should translate the first Kanojo and the second Kanojo differently.
So, TL;DR. It should be "She is also my Girlfriend."