I prefer to use a Bridge vs using her router as the connect point.
I plugged the Bridge to the Router port and launched the App on her iPhone, however the App only has an option to setup up a BOOST ... it asks to press the "infinity" button on the back, but the Bridge has no such button, and pressing the 2 buttons on the Bridge does nothing.
How can I connect the Bridge ... on a new install?
Best answer by ratty
No matter. As I say, Boost superseded Bridge getting on for 5 years ago. Bridge still works, but (a) the controllers may only talk about "adding a Boost" though you can still add a Bridge in the same manner, and (b) v4.0 firmware is so ancient that some additional steps may need to be taken -- i.e. temporarily wiring -- to get everything set up and updated.
As for "killing the ease of setup", I'm afraid this doesn't stand up. You're trying to use a long-superseded device (but which should still work once updated) which is evidently carrying long-superseded firmware. Some extra hoops therefore need to be jumped through. Setting up a modern device doesn't have these kinds of issues.
Just follow the directions posted above. If you still can't get that old Bridge added then you'll need direct assistance from Sonos Support to push newer firmware onto it.