Can Anyone Help?......

I posred an ad in my local newspaper in search of my birthparents. I got a reply but, thiers no way to tell for sure because the lady's sister who maybe my birthmopther is on the run still. There's so many things that the lady and I have in common. Plus my amom slipped twice and said to me" well, I guess now you know you're birth mom is alive" SHE DID NOT TELL ME " POSSIABLY" Anyway I have a first name to the lady that maybe my birthmother but no last name. The lady that called me , I do have her married last name and her husbands first name but not her first name. I would like to find out her maiden name without cost. Where do I this??