Well, I think that I figured it out.
Without editing the part in context I double clicked the feature, not the sketch, and was able to enter the Global Variable and toggle GV and the dimension to see that it was linked.
Poor choice of words on my part. If I double click on the sketch, the part and features in the tree turn blue. If I just double click on the feature it doesn't turn blue but I can edit the dimension...
Just figured out that when I enter the GV from the reference part that the second part wants to create a new GV with the same name.
Not what I was looking for at all.
Still trying to figure it out. If it is possible.
Looks like what you call the "second part" linked to the first one.
Check references for both and break unwanted.
To avoid circular references, have you considered using a part to drive your two parts? You place this part at the top of the feature tree and put the relevant information in sketches that drive the other parts in the assembly. If you need to make a change you can go into that sketch part or use the equation editor (if you name your dimensions, which you should) and change them there. This method is called either the Skeleton Sketch Part or Master Sketch Part method, among other names (try searching the forums for SSP or "Master Sketch" to get a more in depth understanding).
John Stoltzfus introduced me to this method and he's more of an authority on the method. It takes some time to figure out and correctly implement, but the real advantage if done correctly is that you can make MAJOR changes to your assembly or parts at the last minute and nothing should break.
I had a similar situation come up a few months back.
I wanted to link a global variable in one part to another part feature/sketch dimension within an assembly.
I ended up creating a GV in the driven part and linked in to the GV from my driving part.
This was done with in the assembly via:
edit driven part
open equation manager of part being edited
name new GV in driven part
tab to value cell
find driving part in feature tree within the assembly
find GV in driving part within feature tree
select driving GV
link syntax populates
tab over to complete
hit ok to close equation manager
And now my driven part has a GV linked to my driving part GV within this assembly. The GV in the driven part can be used as needed.
Not sure if this was the proper/best way but it has worked well so far.
Hope this might help you out.