You can sue her (I am assuming this is a female) but unless she has serious money it will be a hollow victory. she may have liability on a theory of intentional interference with business opportunity as well as slander/libel. This is a hard case because judges disfavor defamation cases in my opinion and lawyers generally won't work unless you can pay them or there is a pot of gold at the end of the rainbow (contingency case)
Your employer may have acted badly but unless there is some illegal activity such as discrimination or punishing a whistleblower, they can run their business as they see fit.
I am very sorry for your situation. Please note that I am not admitted in ny so I am not allowed to give you legal advice.
Unless you have a contract, you were an at-will employee and therefore could be fired for any reason or no reason so long as it was not an unconstitutional reason such as based on race, gender, religion, etc. As for suing the co-worker, because of the common interest defense to defemation cases you would have to prove she acted with malice. In addition, unless she has significant assets to collect from there is no point in pursuing a awsuit.
I am a former federal and State prosecutor and now handle criminal defense and personal injury/civil rights cases. Feel free to check out my web site and contact me at (212) 577-9797 or via email at Eric@RothsteinLawNY.com. I was named to the Super Lawyers list as one of the top attorneys in New York for 2012. No more than 5 percent of the lawyers in the state are selected by Super Lawyers. The above answer is for informational purposes only and not meant as legal advice.
An employer doesn't need a reason to fire an at will employee. You were there for six months, an d it still sounds like you qualify for unemployment so things are't as grim as you think.
Now, this is where I get serious. Assuming that the bases for termination are bogus as you claim and as you can demonstrate, is there a chance you were fired because you didnt tell them you were pregnant when you were hired (you didn't have to) and/or took time off to have the baby (you were entitled to). If so, you may have a discrimination claim.
If you'd like to discuss, please feel free to call. Jeff Gold Gold, Benes, LLP 1854 Bellmore Ave Bellmore, NY 11710 Telephone -516.512.6333 Email - Jgold@goldbenes.com
You may have a case against the coworker. But legal fees would be expensive, and even if you win, the coworker probably has no assets to pay a judgment. You may be entitled to unemployment benefits.