And less is more.
Don't forget that in this great country (I assume you're in 'Murica), you can buy what you need... anywhere... cheaply.
You'll be wearing the bike gear, when you runout of clean undies and tee's, go to war-mart and buy clean ones. It's the most wasteful thing I do but BIKE TRIP!
Carry a few good quality protein bars and a camelback or 3 liters of water, first aid...
Oh NO! Thread de-rail!! Sorry Ginger.
Sounds like you have the basics done and then some... Do a normal safety check and replace what won't last the milage your riding. No worries, she'll love the trip! Either something breaks, or it doesn't. A couple thousand miles isn't much in the long run. Carry spares of small stuff but be prepared to revzilla or amazon prime anything that breaks that you can't carry. A credit card is much lighter and smaller than a belt you didn't need. Besides every break down is a story (people or machines
)