I still piece with my old Kenmore and just bought a backup at a garage sale for $35.00
All she needs is a machine that will stitch a straight line along with a walking foot.... later on she can get something with a larger throat.
Perhaps it's because you cannot afford a more expensive one right now that makes her wish she had one. Sometimes we think people will think less of us if we don't have the best machine / tools / fabric. Please encourage her to see that her talent will make the beautiful quilts and that 99% of the quilters she surrounds herself with won't care what machine she has (if that is the issue)
You are a very good husband to encourage your wife to do something that she loves.