By 10 he actually means 0.010' which is the diameter of the lightest string, the high E.
All the other accessories are not really necessary aside from a pick that feels comfortable for the player.
You don't need a stand, I leave my acoustic sitting on my couch. You are even more likely to play the guitar if it's on the couch you watch TV with. You play the guitar when commercials come on. That's how I learned the guitar. When you get to the point where the TV show comes back on and you find that you'd rather keep playing the guitar instead of watching your TV show, you've made it.
You don't need a tuner, there are plenty on the internet. I've never owned an actual tuner. If it's a decent guitar, you won't need to retune it that often.
Lowering the action can involve anything as simple as adjusting the truss rod (metal rod in the neck to change how convex or concave the neck bends thus bringing the strings closer) to changing the nut or even the bridge for another one. Axe music did all these for free for me when I had problems with action.
#1 - Buy the guitar - YES
#2 - Buy a case - DON'T NEED (maybe a cheap nylon cloth case)
#3 - Buy a strap - DON'T NEED (is she going to learn standing up?)
#4 - Buy a tuner - DON'T NEED (plenty on the internet)
#5 - Buy a stand - DON'T NEED (prop it on your couch or against the wall in common areas)
#6 - Buy lighter strings - DON'T NEED BUT RECOMMENDED (only costs like $7)
#7 - Lower the action - SHOULD BE FREE WITH PURCHASE
#8 - Labour to have #6 & #7 done and have the guitar tuned. - SHOULD BE FREE WITH PURCHASE
One cool accessory to have however is a capo, that's the clamp that goes on the strings on the neck to change the key of the song up and down in case it is too low or too high for your singing voice.
Regarding humidity, I have seen several guitars warp in Calgary due to the weird humidity and temperature changes we have so maybe a cheap nylon cloth case and a humidifier can't hurt (but you can do with a damp cloth).
What kind of music is your wife going to play though? Do you think she would ever want to play the upper end of the neck (closer to the body). It might be nice to have a cutaway body guitar (the ones with a crescent shaped cut-out by the body) so your hand can reach those notes.