I am someone who takes a long time to process changes in my emotional life so I thought I would reply. You may even say I think in paisley too (or fractals ;-)
I need a lot of alone calm time to feel balanced and not overloaded. I keep learning new skills which helps. But it doesn't change my fundamental desire and tendency to take a slow time with difficult/interesting/new life changes. If CG is like me she may be simmering on a lot of emotional stuff at once including the changes in your friendship.
Since your friendship is a potentially happy new thing that hasn't taken solid shape yet it may be lower in urgency for her compared to her current marriage concerns as previously mentioned by you (I think) and other secondary relationships ending. Perhaps she is just ruminating on your newly expressed interest for a while. This it what I would understand her comments to you to mean. She may also feel strong caution to move slowly with you rather than damage your friendship (and marriage) as you potentially alter/open your marriage for the first time while exploring your new feelings in a way that hasn't been okay or possible before. That would/could take me a long time to consider.
When something big is going on in my emotional life it is very difficult for me to process anything else that also takes a lot of mental bandwidth to consider. With all of the challenges going on for her currently (not to mention the holidays and school stuff on top of it) perhaps she is overwhelmed with having to maintain everything. Perhaps she is currently emotionally saturated and needs some dead air not to process and to just be while she gets rebalanced.
She may be interested in developing your shared relationship further but not be able to process any big changes to it now in her current emotional place. She may also feel afraid of losing your friendship if you decide to emotionally withdraw from her for a while if she says no to you, or if you get hurt somehow, or if she can't fulfill your possibly shifting needs and expectations of her beyond what your friendship already defined.
Right NOW it could be that what she may really need is a good friend (albeit could be flirty friendship may be perfect) as she heals up her marriage. Her actions of breaking off with her secondary relationships makes me think this. Plus, I think you have mentioned that her DH was not too happy for GC to be considering a new relationship with you at this time.This could be part of her hesitancy to move forward. Adding more people to a relationship dynamic that is not in a good place can be problematic. While you and your DH sound good CG and her DH don't.
Is it possible CG just has a lot going on in her life currently but doesn't want to lose you as a friend or possible crush?
I hope my own inward internal thoughts/ideas help
Please dismiss what doesn't fit.