Oh, I see, didn't understand, but i see what you mean.
If the whole thing is going to be the girl's voice, then it is possible to switch tenses betwen paragraphs. i assumed when i made my first comment that it was going to be all one 'stream-of-conciousness' delivery.
So, you can swap tenses inbetween paragraphs, but not in the individual paragraphs - so you can have -
"I'm floating on a cloud and i feel as free and alive as i have ever felt in my life ..."
"Back then it was all different, when i was younger, and felt so well all the time, i took it for granted ..."
see the idea?