SIL finally answered us. Best we can get out of her is she wants a good older solid machine with easily replaced parts if needed. Doesn't have to be a ZZ but does have to have reverse. And has to use low shank attachments and accessories.
So I'm thinking of a 15 or later 66.
Also turns out she's got quite a few machines so she knows where to go to get them. I didn't know that till last night. If I see something she might be interested in I'll tell her.
Joe