Will I be able to get my money back?

You are mistaken that there was no contract.  You had an agreement with this woman that you would pay her $2,000 apiece for space at two expos.  That is a contract which probably did not have to be in writing.  The question is whether the two of you ever agreed on whether you had a right to back out.  If this was never discussed, you probably have no right to back out.  HOWEVER, in most cases a party aggrieved by a breach of contract has the obligation to mitigate their damages.  In other words, while you may have no right to back out of your agreement, the other party may be required to mitigate her damages by selling the space you were going to use to someone else, if she can.  Her damages would be reduced by whatever she can get for the space.  In other words, unless your agreement expressly provided that the money you paid was non-refundable (and maybe even in that instance), and even if you have breached the agreement, the woman would be obligated to return to you any money she can get for the space from someone else, so that if she were able to sell the space to someone else for $3,000 total, she would only be out $1,000, and would be obligated to return the remaining $3,000 you paid her.