Hello, the idea is that you can use the license on all Macs you own, i.e you are working on. So if you have a desktop and laptop, or home mac and office mac, the license is valid for both. But your wife's mac is not the mac you use, so you would need another license on it. There is a family option when you purchase the license, this will make the license valid for 5 family members.
I hope this helps,
Rgds
Zsolt