Galen,
You've got a lot on your plate, Son, what with your daughter and this with your wife. Went through that myself, the sleep apnia. Because the body fights to wake us up, cause of airway restriction, we never get good REM sleep and never recuperative sleep. Tends to wear down the body and organs... MS is also a "degenerative" disease, not infectious one, so who knows what leads these things to occurr.
Testing and the modern approaches through appliances really help. I used one for 2 years and for whatever reason, dont' seem to need it now. I'd encourage your wife to confront this...by comparison, Sleep Apnia is a cake walk compared to fighting MS...and might help her body fight the effects by allowing her more sleep and recuperation.
Blessings on you both and prayers that your wife accepts this new challenge and walks in Faith to challenge it.
Lord, in your mercy...