Sue roommate for unpaid rent time limit

I rent an apartment in NYC. The lease it at my name, and states that I've roommates that help me pay the rent but I'm the one responsible to pay the entire amount to the landlord. A little less than 2 years ago, after almost one year living in my apartment, I've a roommate that I thought was a friend that left and owes me over 4000 dollars unpaid rent. As I thought we were friends we never wrote any type of signed agreement, but I've the text communications as well as rent payments on my bank statements as she always sent me the rent through bank transfer. As far as I know this would be a small claim court type of claim. My question is how long do I have before it's too late to sue this person?