Ordered that the order is reversed insofar as appealed from, as a matter of discretion, with costs, that branch of the plaintiff's motion which was for leave to serve a supplemental complaint adding additional allegations of cruel and inhuman treatment is granted, and the plaintiff's proposed supplemental complaint is deemed served, and the defendant's time to serve an answer to the supplemental complaint is extended until 20 days after service upon her of a copy of this decision and order, with notice of entry.

Pursuant to CPLR 3025 (b), a court, in its discretion, may permit a party to amend or supplement a pleading at any time upon such terms as may be just. If the adverse party fails to demonstrate that the proposed amendment will unduly prejudice that party, the court should exercise its discretion in favor of the movant.

In the instant case, the defendant wife failed to demonstrate that granting the plaintiff leave to serve the supplemental complaint would unduly prejudice her. Accordingly, we find that Special Term should have exercised its discretion and granted the plaintiff leave to serve the supplemental complaint. Mangano, J.P., Eiber, Kunzeman and Harwood, JJ., concur.