If she is going to spend a year there and leave her current life, that's nothing to do with a relationship naturally breaking up, it does sound more like excessive devotion to a particular spiritual practice/teacher.
Possibly inadvertently, you have hit the nail square on the head here. Usually when someone withdrawls from their life situation so suddenly and completely after joining a yoga group you often find that in their practice of yoga stands a guru teacher they are devoted to and manipulated by.
I've done yoga on and off for years and by far the most 'enlightening' classes were the ones who concentrated on you finding out for yourself what parts of the practice helps you attain your own physical, emotional and spiritual well being. In those situations there was never a head teacher/guru type person whose philosphies you were encouraged to take on and show devotion to.
I know I sound a bit like a hornet blower with the few posts I have done here mostly centred around this aspect.... But I truely believe that the minute you take dramatic changes after joing any group you need to have a good look at what is really happening and why you are doing this and your motive. Brainwashing by a 'spiritual' guru, even if the guru isn't the one running the classes, but is one who started that partcicular School of Yoga can often be extremely subtle and almost go unnnoticed for a long time.
For most people who do things like yoga and meditation their initial aim is mostly to find relaxation and ways to cope and deal with what is happening in their lives and enhance it... Not to suddenly up and walk away from it all... I'm not sure if I even successsfully made a point here... but I tried... lol...