As Fruit Bat /\0/\ states, or possibly understates, the web based ones can be pretty poor. I once tried the Google version to write a short note in German to a genealogy centre in Switzerland. They replied (Embarrassingly in very good English) that they could barely understand any of my request and could I please re-submit via a German speaking translator. Good luck, and sorry I have no useful suggestions
Computers cannot understand language or grammar so, of necessity, the results of any language translation will be less than perfect and sometimes a complete joke.
To illustrate, try translating some English text into German then from German into French and then back into English. What comes out will usually bear little resemblance to what you started with and the more languages it goes through, the less sensible is the final result. Sometimes it can be very funny.
Rather than cause herself embarrassment your wife should stick to English or, perhaps, learn German. If she did the last, having a German friend would be great for learning real idiomatic German - the way it is really spoken rather than what language courses tell you is spoken and written.