The quotations start from when Jim tells Laura about Betty, his girlfriend. They include Extended stage directions and dialogue for both Laura and Tom.
Well, I'll play the other side for a few minutes. When Laura gives the unicorn to Jim, perhaps she is signifying she no longer needs the symbol of what she was--a unicorn, a mythical creature, an oddity.
In those final stage directions we see a crumpled Laura being comforted by her mother. There has been a loss, actually more than one loss, and her reaction is perfectly understandable. However, at the end of the speech, it says Laura "lifts her head to smile at her mother." So, even though the blowing out of candles is generally symbolic of a death or a loss, I can see a scenario where this is a farewell to the "old" Laura and the beginning of one which is more hopeful and confident.
I think there are two main quotations that suggest what will happen to Laura, The first is when Jim is about to leave and Laura gives him the broken unicorn. When he asks why she is giving him the gift, Laura's only reply is "Souvenir?" The unicorn represents Laura and the broken horn represents a time when she seems normal. However, since only the 'souvenir" remains, I think she is saying she will only remember the event, not change from it. The second quotation occurs at the end of the play. Tom is talking after the action is over. He turns to the stage and says, "Blow out your candles, Laura.' The candelabra is another symbol for Laura. It is bent and deformed just as Laura thinks she is. However, the candelabra glows only during her scene with Jim. The action of blowing out the candles also signifies that her desire for normalcy was "snuffed out" when Jim left. Thus her live will not change and she is probably destined for some kind of institution, like Williams own sister.