Honest Advice please girls....(guys cn reply too)?

From the way that you put it, yeah that new guy is just a rebound. Don't get your hopes up though. You can't expect her to come running back to you because things can change. So it's better to just be chill about it without worrying about what she's doing or who she's with too much. If she does eventually go back to you, then great! Just don't wait for her because you could be wasting your time.