First off, if you have to brew in the shed, it will be no problem. But once the brewing is done and you have your wort in the fermenter, you should move it back into the house where it is cooler. As others have mentioned, fermentation rarely makes a noticeable odor (apfelwein and some lager yeasts exempted).
However, if she wants to complain about a couple of hours of boiling grain and hops, she is certainly not willing to make a very small sacrifice in order for you to get some enjoyment out of life. That's my opinion.
I mean, how often do you plan on brewing? Once a month? twice a month?
Moving the brewing to the shed is not a big deal and many would actually prefer it, but IMO it's not a big deal to put up with the smell of brewing for a couple of hours a couple of times a month. Maybe she could go off and do something and leave you to your hobby during that time.
I would prefer to brew wherever the tools best for brewing are located. Kitchen faucet, better lighting, drain...