When you have a vehicle of that size in a bike shop it takes up a lot of space, it is super hard to get it in a stand if you can and is a pain to work on. When they can see that, the bike is the wrong fit for the person they will probably also be less motivated to work on it. You are acting as if this is just a normal bike getting normal stuff done. This is a massive trike with a huge wood cargo box in the middle as well as a full electric system. At the old shop I worked at we had the space and mechanics to work on it but it was still a massive ton of work but at my new shop I have no space for that and wouldn't be able to work on it easily. Also there are still some shops that haven't really done much with belt drives and might not have all the tools and knowledge for it and making such a drastic change to a bike is not something a shop less familiar to Gates would probably want to do.

I think moving is probably not the way to go as that is way more expensive I would probably get a lighter-weight more maneuverable bike (not a trike) with a Bosch Cargo motor and that would help greatly. It is not what you want obviously but this shouldn't be about you it should be focused on her and unfortunately that trike is the wrong vehicle for a hilly area.