Congrats on getting out for the ride! A "piddly little 13 miles" is many universes longer than zero miles. Better yet, running into that "fixer-upper" Terra Trike for a hot price is a dream and the fact that you're capable of fixing it up and getting it roadworthy yourself (no kick-in-the-head LBS overhaul bill) makes it a lifetime-quality dream! Sounds to me like that 13-mile ride was a better ride than any that I've enjoyed in years on end.

Hand in there with your mother's situation. It will run its own course in its own time and all you can really do is what's needed/expected of you and going with the flow. Best of luck with it and enjoy the new trike too!