I was afraid to say what I feel because I don't know how she will react

To tell you the truth, wow that's too soon for someone to get over someone else that fast after that long, either she was not serious with him and there relationship was whatever, or she bullshitting her self and getting with you so she can feel being with a guy again. but if you want to tell her just tell her. but not in a freakish way. in and adult way. sit her down after going out to a movie or something and then tell her after when you guys are hangin out somewhere. but another thing is that she is 21 and ur 19. you wouldnt be able to go places she would want to party with you at. so its tough.

But to me I'm sorry to say because I'm an honest person and everyone who knows me always asks for my advice but unless she gives you good reason of why she like you so much then your just a tool til she finds someone her own age.because ive been in this situation. where I was that girl.

oohh... Bad move, never start a relationship with a lie becasue then it will all be based on a lie and there will be no trust. My advise, tell her sooner rather than later. The sooner you tell her, the more she'll understand.