Most of the high points have been covered.
+1 Warm beverages and extra calories, and while it's not light, the thermos full of hot chocolate.
Remember that there's usually a 10-15 degF difference between the EN Comfort (woman's rating) and Limit (men's rating) for a sleeping bag. The mfr's rating for most bags is at or below the EN Limit, so the extra 15 deg you mention is not excessive.
Looking through the litany of layers, the warmest thing on her bottom is fleece pants. Additional insulation south of the equator can make a big difference, so how about adding down or synthetic insulated pants?
You mentioned a balaclava, but if the UL down inner doesn't have a hood you might consider a separate down hood, or maybe a Ray-Way Bomber Hat http://www.rayjardine.com/ray-way/Bomber-Hat-Kit/index.htm. I got a buddy of mine one of those for Christmas; he says it's amazingly warm, and unlike my BPL Cocoon balaclava it offers good peripheral vision.
I've been experimenting with a vapor barrier suit for sleeping below 25. On a recent trip I took my Phantom 32 bag to about 5 using a MYOG bivy, the VB suit and a modest selection of additional clothing. Assuming she's pretty sedentary in camp, she could try a VB layer over her base. Someone her recently mentioned having AGG make a custom top and bottom; I went with the gray Warmlite "fuzzy stuff" http://www.warmlite.com/vb_shirt.htm pants and shirt at 5 and 5.5 oz, respectively, which loosely resemble cheezy scifi B movie attire.
You could fill a Platy or Camelbak bag with heated water and have her sling that between her base layer and fleece. If you already have the Platy then all it costs is some extra fuel.
As a last non-UL possibility, what about a liquid fueled handwarmer like http://www.zippo.com/products/handWarmer.aspx?bhcp=1 again carried next to the torso?