Extension of marriage visa, does my wife have to come along?

Wouldn't you check with the relevant Immigration office? What good is it if you get the answer here that it is not necessary, but the office in question believes that it is necessary?

I think she should go. In addition, it is always easier to talk when there are ambiguities. Make a day out of it.
Otherwise, call the immigration office first. Can you immediately ask if anything has changed.

Do wonder what the problem might be having to take your wife with you? Finally, it is also common that, with a year extension, based on marriage, you will receive a stamp 'in consideration' for one month. During this month it is not uncommon that you will receive a visit from the immigration police at home to check that you are not only married, but also cohabiting.

Is a decision by your immigration office whether your wife must be present at the application or not, but almost everywhere they will say that your wife must be present. Also for follow-up requests.
So it is best to inquire locally.

But actually that is not that important when submitting the application, if that immigration office works with an “under consideration” stamp of 30 days.
After all, that stamp gives immigration 30 days to check whether the marriage is “de jure et de facto”, in other words that you are not only legally married, but also live as married people in practice.
That is why they also come to take pictures, to check whether you are indeed living together, to carry out neighborhood investigations, to witness, etc….
Each immigration office has its own procedure for this that it follows. There are no official rules for this.

There are also immigration offices that operate without this “under consideration stamp”. Then sufficient proof must be provided with the application that you are married and live together, of course.
Here too, each immigration office will follow its own procedure. It goes without saying that in that case your wife must be present during the application.