Unfortunately, I don't know that there's much you actually can do. Sleep apnea needs specialized intervention (those Breathe Right strips won't do much, if anything) and that intervention will take time.

My husband has sleep apnea and the only thing that helped was getting him fitted for a special mouth piece he wears at night - it pushes his lower jaw forward to keep his airway open. That, or a CPAP, are the only real solutions I'm familiar with.

However, if she had a severe illness & her health has continued to worsen, there may be something going on beyond sleep apnea alone. At any rate, a prolonged period of feeling like death-warmed-over takes its toll on a person, so try to exercise your compassion/patience.

In the mean time, you guys should talk about balance. For you - it means managing your expectations for what she's likely to have energy to do. Staying up until 2 a.m. all the time definitely isn't going to work, and it's reasonable for things to cool off in the bedroom.

For her part, she should make an effort to rally. Feeling crappy is tough, but she should still be able to acknowledge that it doesn't give her a pass to take it out on those around her. I recently had a tonsillectomy (i.e. two weeks of misery) and I certainly got unpleasant at times. At those times, my husband would say something like, "I think you're in a bad mood" or "You're cranky right now," as a signal for me to check myself. It was then my job to apologize & either focus on being pleasant, or if that was impossible, excuse myself to go take a nap, etc.

At any rate, ask her what she needs from you and do your best to follow through - even if that means she needs to spend less time with you. New relationships take a lot of work and there may be times when she just needs to be alone. Also, talk with her about what you can both feel comfortable with in terms of letting her know that she's over the line with snapping at you - how can you let her know she's being mean, without you being mean in return? That bit takes some fine-tuning, so keep the communication lines open there.