Not a lawyer, but Guide to New York Evidence
https://www.nycourts.gov/JUDGES/evidence/5-PRIVILEGES/ARTICLE_5_RULES.pdf:
A husband or wife shall not be required, or, without consent of the other if living, allowed, to disclose a confidential communication made by one to the other during marriage.
CPLR 4502 (b). The spousal privilege protects confidential communications induced by the marital relationship...Separation of legally married parties will not necessarily preclude application of the privilege
The best practical differentiation I can see online for communication versus testimonial privileges follows, and it seems like she in the end would still enjoy a lot of protection:
-The spousal testimonial privilege which applies only in criminal cases lasts only as long as the marriage does. Additionally, the privilege belongs to the spouse who is being asked to testify. Once a couple divorces, a former spouse can no longer invoke the privilege to avoid testifying in a criminal case, and the other spouse cannot assert the privilege to prevent that testimony from being admitted into evidence on the basis of the privilege
-The marital communications privilege applies in both criminal and civil cases. It only covers communications made during the marriage. Unlike the spousal testimonial privilege, this privilege does not end when the marriage does. Either spouse can assert the privilege long after a divorce and prevent the admission of testimony pertaining to confidential statements made while the parties were married.
It looks like she could be compelled to testify but why bother if all the communications she'd be testifying about are protected under the communications privilege?
And just noting, there's an interesting article from St.John's Law Review entitled "CPLR 4502(b): Spousal Privilege Does Not Extend to Conversations Which Advance Joint Criminal Activity" (Just putting that out there.) It states "Moreover,
the testimonial privilege is designed to promote socially desirable goals, and a joint attempt at criminality obviously is not desirable behavior; to hold conversations furthering criminal conspiracy privileged because the conspirators happen to be married would "require a finding that. . . the commission of a crime would
protect and strengthen the marital bond."
I think this is the adverse spousal witness privilege. Seeing this:
New York has an adverse spousal witness privilege:
-Privilege belongs to the witness spouse
The witness spouse can choose to assert the privilege and prevent the other spouse from testifying against them.
-Privilege can be invoked after divorce
The privilege can be invoked even after a divorce if the communications were made during a valid marriage
Am seeing this was adverse privilege was supposedly pretty much done away with by the
Trammel case with the Supreme Court-- but not completely. That's something to watch for down the road, for sure.