If Romeo had packed up and left, do you think Juliet would pick Paris to keep her life together or would she wait for Romeo to come and take her back?
I don't believe Juliet would have accepted either of these propositions. She would not have married Paris, nor would she have waited for Romeo to return.
Even if Friar Lawrence and his potion had not been available to her, Juliet would have found some other way to escape from her family and Verona and joined Romeo in Mantua. Perhaps that would have been with the help of the Nurse or someone else unknown to us, but because Friar Lawrence presented the best option that is what she went with.
Juliet reveals her impatience throughout the play. And from her character I think it is clear that Juliet would not have stood idly by waiting for the situation to work itself out; she would have taken action.
I'm a little confused, because Romeo did pack up and leave Verona. And Juliet did not pick Paris...
When Romeo gets exiled from the city after he kills Tybalt, there is no way for Juliet to know that he is going to come back for her. She could very well have married Paris the way her parents and even the nurse want her to. But she did not.
So it seems likely to me that she would have waited for Romeo for some pretty serious length of time. I imagine she would have given up on him eventually, but it would have taken a while, I would think.