Pop quiz: Peter's mother-in-law did this because:
a) Peter's wife was away on business, marketing the latest catch to fine Roman restaurants;
b) Peter's wife was a lazy bum who didn't like Jesus or wanted to make a fool out of Peter and thought so little of her fever-ridden mom that she let her take care of the guests; or
c) Peter was a widower.
EXTRA CREDIT: Name, with Scriptural citation, the wife of any other apostle. Five points for each. Take as much time as you like.
The fact that Peter's mother-in-law served Jesus and the apostles does not mean that Peter's wife or anyone else did not serve them. It's not an either/or situation and your logic is faulty. Her actions are probably mentioned to emphasize that Jesus' healing was instantaneous and complete. In other words, there was no "getting well" period -- she was instantly as good as new.
There are no scriptural citations as to the names of any of the apostles wives. However, Eusebius in Historia Ecclesiastica III says that the apostle Philip had three daughters and that the grandsons of Judas Thaddeus were sent to Rome for martyrdom, but sent back when the judges saw their calloused hands.
According to Catholic Saint's Online:
"St. Petronilla is believed to have been the daughter of St. Peter. Until the XVII Century, she was called his physical daughter, and since then, she has been thought a spiritual daughter who was consecrated to his service."
Interesting, isn't it, how the early church viewed her as a physical daughter until pretty late in the game. If you were to do a bit of research, you would find out that some of these "traditions" aren't as old as you think they are.