I am pretty sure what
geo1005 was saying is true - and he was right to spell it out. Upgrades that you get when you check-in or at the airport don't give you the bonus miles... I thought that is what you were alluding to when you said that "
(as any other award or class upgrade wouldn't count)" - but it did surprise me when you said that you could only purchase the upgrade at T-24...
Assuming that you can get a bonus points earning flight at T-24 - well PHX-MSP doesn't seem elite heavy - but it is the holidays... Also unfortunate that MSP doesn't seem to have any short hop flights nearby (I was hoping that you would say somewhere like BLT - where your wife could get a cheap o/w and you could drive and meet her at the other end....)
(On that note - your wife might want to take
a one-way to Tucson for $110 - $130 and you could drive and meet her... it wouldn't be cheaper than a Las Vegas rtn - but at least you might be able to make a day trip out of it.... )
Also getting an extra segment into the PHX-MSP flight is going to be a push...
It is such a shame that the dates are so tight. The points from the last flight will likely post on the 26/27th. And I think that if you were to call on that day - there would be a good chance of your wife being able to slip through to silver given the circumstances. But if it were not to happen - then you might well be stuck with having to buy a considerably more expensive last minute flight. (I looked at having a security refundable ticket to LAS and from the prices I saw it would be cheaper to buy up..)
I think that your best bet is
i) To try sweet talking for No change fee for a bonus point gaining 1st class ticket
ii) Booking a LAS mileage run
iii) Making a day trip to TUS
or crossing yr fingers and hoping for
a) Bump on PHX/MSP flight
b) Sweet talking US DM forgiving the extra 43 miles
c) and failing a) & b) hoping that ii) and iii) are not last minute really expensive that your final option is
d) Buying up