So we decided to install an AMP Research Powerstep. It automatically opens and closes with the doors.
It works great! She can now enter and leave Annie all on her own!
I won't describe the installation, because the step is specific to the Transit, and comes with excellent instructions. But I did take some proof of concept pictures.
The step is almost invisible when closed:
But you can see it fine when opened:
Then she experimented with entering and leaving:
It even gets the aesthetic committee's seal of approval!