Smart devices should be set up on one Alexa account. That way any person in the house can just say "turn on xxx light" and it will work.
It is possible to share a smart device (e.g. light bulb) by using the manufacturer's app and sharing feature (if it has one). For example, the Wyze app allows the account owner to share a Wyze Light Bulb with another user. Using the Wyze app, you can send an invite to another person. Once that person accepts the invitation, they can control the Wyze Light Bulb that is shared with them. After it is shared, they have app control. But that does not necessarily mean that it is visible through Alexa. That's another layer which may or may not be available to you depending on the device and the manufacturer's implementation. This is different for every smart device manufacturer and some might not have sharing at all.
This is way too complex to do such a simple thing as turning on/off a light bulb. Easiest way is to just set up all smart devices on one account. Giving that the other user is your wife, why does it matter who owns that device and what account it belongs to? If you want to turn on the bathroom lights, it shouldn't matter if that bathroom light device is on your account or on her account. Just put it all on one account and say "Alexa, turn on bathroom lights."