mac – Using A Different Timemachine Backup

I have 3 macs (mine, my wife’s and an Extra), all running 10.15.7. I use a TimeMachine Capsule to backup all three over my home network.

The other day the logicboard in my wife’s died and it’s not worth fixing.

I would like to use the Timemachine backup from her computer and use Migration Assistant to install it on the Extra mac. This way I can get her up and running again. When I go to use Migration Assistant it will only show me the Extra computers TimeMachine backups.

When I login to the Timemachine Capsule server via my Mac I can see all three backups.

How can I get Migration Assistant to recognize my wife’s Timemachine backup and install it on the Extra computer? Or conversely can I use the Timemachine backup file in another way get to the same thing manually?