Indeed it is, but it is the pastor's responsibility to clarify her role with the Board or Call committee right from the start. If she has a defined role, great, but it needs to be specified up front, and paid for. If she is to be just another member of the congregation, she can for sure bake cookies and do whatever other members do. I would question why a preacher's wife would want to attend a different church, however.
"I would question why a preacher's wife would want to attend a different church, however."
Because she (actually, the spouse isn't always "she") need her own pastor, just like the doctor's wife needs her own doctor. Generally, doctors don't practice on their family members, and clergy should take the hint.
Second, she needs her own faith community where she is "just a member of the congregation." This is impossible when they are the spouse of the pastor. Just try praying when the people in the next pew are making fun of the pastor for a gaff.....