I must admit, I'm not surprised by your W's change in attitude...not that you've done anything, you haven't. BUT, I notice you said she's stayed at SIL's house again lately...she has become fairly predictable in the fact that when she stays over there...she becomes more distant.
Chances are OM has also started applying pressure again...possibly a drop-in again. Hang in there...wait this out if you can, but maintain what you've been doing...because you are doing all the right things. She may also be backing away again because she's caught herself feeling things for you again...and that's probably felt like she's setting herself up for failure again...she still doesn't trust your changes.....or her choices where you are concerned.
Try to hang in there bud!!! It's not over yet! GEL