I'm partial to the Dahon Curve D3 myself. It might be more expensive than some other folding bikes, but the quality is there. I've actually considered a Citizen Tokyo, but after seeing a Citizen Gotham 7 I changed my mind. Looked somewhat solid, but seemed the components were a bit lacking.

Check out the Curve D3, see if the Mrs enjoys it. Me, I wish I could get my wife to ride with me. No deal,... Sigh,...