subleasing problem

I may have to be involved in a lawsuit. My subtenant did not pay me a penny. She made excuses one after another to delay the payment. I send her emails,
she keep on ignoring my emails. But the problem is WE don't have any paper works. though she admit in the email that she will pay me someday. In addition, she caused great apartment damage during her stay. Should I sue her. How much will it cost me? How about the chance to win the lawsuit? How much the lawsuit will cost?

I wonder if there is anyone having the similar experience.
: : :
: : : Please advice me.
: : :
: : :