With the time, effort, and emotion invested in a relationship, it is considerably difficult when someone asks for space in the relationship.
A relationship needs the love of two people, not just one. Unfortunately, no matter how much you love her, you can't convince her to be in a relationship with you. She may have to experience life without you for a while before that happens. Her saying that she needs space and that she is not sure if she wants to be in a realtionship now shows that she is not wanting to commit to a serious relationship. You both have to want the relationship. If either of you are not ready to go to that level, the best thing to do is continue giving her the space she needs so that she can come to terms with whatever it is that she is dealing with and when the moment is right for you both, everything will fall into place.
Don't force this relationship. Something in her life is making her need some time to herself. Trying to initiate contact (by any means) with her when she is wanting space will only make it worse and can actually set you back further. It is better that you not buy the engagement ring until after you talk with her.
If you are uncertain, ask her to clarify two things (otherwise you'll stay pretty much stuck in the same place and won't ever come to a more final term in your relationship): what the terms are for taking a break in the relationship (what form of contact is she comfortable with and how often--it should be fair to you both), and whether this is a temporary break in the relationship or if she wants it to be over. She knows that you love her and that you aren't going anywhere, but at the same time, you need her to be honest with you and let you know if she doesn't want to be in a relationship with you right now. You want this relationship to work, but she has to want that to.
If after talking, she decides that it is best to end the relationship, you can only respect her feelings and accept that for what it is and move on. In any relationship, there is always the chance that there will be a reconcilliation, but you could be waiting for a long time and get your heart broken even more.
In the meantime, help yourself by doing a number of things. Share your feelings. Some people find that sharing their feelings with someone they trust helps them feel better. Keep yourself busy. Sometimes this is difficult when you're coping with your emotions, but it really helps. That doesn't mean you shouldn't think about your relationship; you don't want to mask your emotions and not deal with them. Working things through in our minds is all part of the healing process; it just means you should focus on other things, too.
Sometimes people start to blame themselves for what has transpired. They may be really down on themselves, exaggerating their faults as though they did something to deserve the unhappiness they're experiencing. What happened in the relationship and what made her need her space is of no reflection on you, your desirability, or your worth.
You have lived the past couple months without her in your life and you are improving with each day. One thing you will notice when you truely begin to heal is that you realise that you are no longer thinking of her all the time, but when you do find yourself thinking about her, it doesn't make you feel sad, angry, hurt, bitter, etc. If thoughts can come and go freely without bringing you down, and you are able to remember the "good times" without them eliciting a painful emotional response, then you are most certainly on the right track.