Yes, Jill has that shirt in the game. And so could you! Sukeban games sells the shirt as well, or did for a bit. I came very close to buying it, but you can only wear it in certain situations.
There is an interview with the writers where they claim that they didnt include any "i love you" scene because they thought the viewers would find it an insult to their intelligence (as in "No duhh! Tell me something i dont know")