Spousal privilege only applies to things that one spouse said to another. It does not apply to things independently observed by the spouse. The answer is really no, wife does not have a right to refuse to give a deposition concerning her husband. She can, however, refuse to disclose things husband said to wife, assuming they were confidential.
It also depends what the issues are at the deposition. For example, if a husband is suing and part of his lawsuit includes a loss of consortium claim, then no.
There are a lot of variables when it comes to spousal privilege. In this hypothetical scenario, the wife should consult an attorney to go over the specific facts of the case to determine whether any of the communications are privileged.
Since your question does not provide much by way of background, this response will more general and attempt to add to the fine answers already given above. The spousal privilege does not mean that a spouse can refuse to testify. It refers to a limited privilege relating to private conversations between spouses during the time of marriage. While the privilege may provide that a spouse may not answer a given question relating to a privileged communication, it does not protect the spouse from having to appear to a properly noticed or subpoenaed deposition. Depending upon the individual facts, the spouse may wish to file a motion for a protective order to limit the scope of the deposition or perhaps, under the right circumstances, quash the subpoena (if a subpoena was utilized).