Well, I'm 68 years old. I'm still using the machine my husband bought for me for Christmas in 1963. It is all metal, has cams for decorative stiches, and I've sewed sooooooooo much on it, I'm sometimes surprised that it's still going. I've learned to take it apart (the tensions) and clean it up myself. It's only been in the shop once in my memory and it still sews up a storm.
That being said, if your wife doesn't have a machine of any kind, then I would suggest she start out on a relatively reasonably priced machine. I have eight or nine machines --most of which I've inherited. Not a one of them is newer than the 1980's. I have the buttonhole stitch cam, so I can do machine applique also!
I hope you continue to encourage your wife's creativity. Research the bells and whistles she really wants -- they can be found in fairly inexpensive machines. My 1963 Singer 328K only cost $150 new from the Singer dealer!
Best wishes. Encourage your wife to join this board. Many of us use the "vintage" or even antique machines!
God Bless.
Jeanette Frantz