Varnish without a doubt, see how the bony areas are remaining dark while the rest of her coat is going lighter (for example up her nose-bone in this picture below
Varnish is a "fun" to a point, some horses it affects almost immediately while some can take YEARS, but the downside to varnish is that with time it tends to "wipe-out" the other pattern(s) the horse carries and many go white..
Here's my varnish roans:
Black based varnish snowcap mare, was black with snowcap to withers but as you can see has gone mostly white, but still keeps the darker lower legs and the dark areas on her nose like your mare:
Her 2007 colt, who has gone completely white (except for the nose bone and lower legs), believe he got a "double dose" of varnish as both sire/dam are varnish roan appaloosas:
Her 2006 colt, a bay varnish snowcap, he too has gone pretty much white:
One of our stallions, black near leopard varnish appaloosa plus splash (he too is registered as a blue roan, but not possible since neither parent is a roan)
As a foal:
Now:
This is one of our 2008 colts, he's sired by the above stallion and is out of a black tobiano/splash mare.,. He was born solid black but with time has developed (what I call) frosting/snowflaking over his hips (and possibly spots!), right now it doesn't appear to be affecting his face so not sure if it's varnish gene coming through or another pattern, hoping by luck he didn't get the varnish gene and he does spot out like his dad, who as you can tell by the pictures above he went from a spotted blanket to full blown near leopard (and keeps getting more and more spots year to year!)
Foal:
Most recent:
