My W goes from working on our R then uses that she needs to work on herself before she can work on the R. Is this just an excuse or is this a reality for her? I want to work on the R and myself at the same time

Your W is the one making the most sense here. Sounds like she sees stuff in herself she knows she has to work through first before she can be any good for the relationship.

And if it turns out to be that it's a stall or an excuse, you'll find out soon enough. Watch actions instead of wondering about intents.

how can you move forward as one falls apart and the other gets better?

Doesn't a fever break AFTER it gets worse?