I'm only "wondering" why ... not "having to know" why. It's different.
You are right it is different and it is a positive step for you.
That said, it is still pointless to wonder why. Even if you figure out the first why you'll never really get to the 5th why (or root cause) so why waste your time and energy? Don't even THINK about asking her why. Even if she tried to answer, she probably does not consciously know the REAL answer anyway.
Her emotions and thinking may be all over the place. One minute she may think about coming home to you and the next minute she may resolve that it is over for sure. THAT is exactly why you cannot and should not use her immediate reactions to judge if you are doing well or not. You need to develop that feeling for yourself.
Be a Rock.
Good Luck
But what is happiness except the simple harmony between a man and the life he leads? ~Albert Camus