My girlfriend wants to take a break in a 3 months old relationship. She liked someone else who rejected her and I appeared in her life too soon, while she was still recovering. She likes me a lot, but she doesn't know if she loves me. She also thinks we should've had more romance and time to get to know each other before we began dating. There's the possibility we, in 3 weeks time, go on holidays with friends. I'm afraid by accepting this break and then going on holidays I'll become just another friend, but I'm also afraid, if I don't go, I might miss the perfect opportunity to reconcile. What to do?

Break most often means break up.

It seems you were her 'shoulder to cry on',and now she wants to move on.

I would go no contact-no communication at all and start living my own life.

As for the holiday,bad idea,save your money.

She wants a break so, give it to her. Sucks being a rebound but, bow out , move on and look forward to better opportunities.
Saying she wants a "break" is just a way of letting you down easy... no one intent on creating a successful relationship takes a "break" to deal with problems. So,why worry about reconciling with her. Let her go, if anything this has been a good learning experience... take heed of tortured souls.

Give her what she asked for, and make your own holiday plans without her.

Sounds a lot like you were her rebound. Now that she's done rebounding, she's reconsidering the relationship.

She already knows that you want a serious relationship, so the ball is on her side of the court. If she wanted the same thing, she would let you know.

As tough as it is, I suggest that you go do your own thing and let her come to you. You can't force her to come back to you, she has to come back on her own terms.