In reply to benji:
Firstly, congratulations
Secondly, I can't comment specifically on altitude, but, as you've said, listen to her body - you may find that, if she's anything like my wife was, she'll be so nauseous at times that she won't want to do anything and will be so tired she'll want to be tucked up in bed by 9pm.
Best advice I can give her is to have a stash of biscuits handy - regular nibbling helps keep the nausea at bay.
Post edited at 13:19