The traditional thing to do is buy your seat for cash so you get the EQM and spend your miles for her seat as a pure award (depending on how "traditional" you are you may want to swap that around of course). That works out to fewer miles but even more cash.

You could just buy the missing 20k for $750 and then get two awards. You would be out 220k miles and $750 instead of 120k and $4400. So you would be getting 3.6cpm on the extra 100k.

Alternatively, depending your ethics you could purchase SWUs from a stranger on the web for not much more than the copay and save all your miles.

Or for $1,575 you could buy 90k US Airways miles (with their current 2x perennial promo) which is enough for a return flight to China on their programme. But coordinating two rewards with two different programmes can be a pain.