I'm in the process of divorce I was married for just under seven years I live in NY state and my wife had a child from a previous relationship she claims that she can order judge to make me pay child support how is this possible when the biological father is known. And not paying support

While it does not happen very often, it does happen at times, if a step parent was acting as the parent but the bio parent was no where around.

They will aruge you took the role of parent and acted as such.

She can not "order" the judge she can make a motion in court, argue the facts, you make your defense and the judge will rule.

Is she doing this as some black mail to make you do something

Depends on where you live it might not even be possible. If it is possible where you live, there are a number of requirements that must be met in order to assign support.

She cannot order the judge to do anything and if she does, it will amuse you how badly it ends for her. She can ask nicely and hope a lot.