Flicker 20/30 YF Kid's Sleeping Bag

Feathered Friends has short bags for women. Temp ratings are spot on. The YF bags save $$ over the UL for very slight weight increase. They also have a kids Flicker; 5ft hoodless bag that can unzip to quilt. I have a regular YF 30 that I love. Worth a phone call. 

Feathered Friends Flicker is a great quilt. Expensive but worth it and great for hammock camping too.

My FF quilt is the best purchase I have ever made, absolutely incredible. 20 degree and yet still sleeping with the toe box open below those temps

I also have a Flicker, but the lack of a hood and draft tube gives me a similar experience as yours in colder weather. I use a Western Mountaineering Alpinlite (also rated 20 degrees) for those conditions, it's \*much\* warmer. It's a "roomy mummy", not constrictive, won't compress layers, a pretty good way to transition from a quilt if that's your jam. I think efficiency is more than the oz. of down, it's also the design and cut, which makes comparing bags difficult. The Flicker was OK to about 30, I've been warm cowboy camping in the Alpinlite to well below freezing.

I got a deal on a Feathered Friends quilt. Thick goose down that’s comfy well below freezing. I love it, but I could never afford retail on it. Take a look on used markets for something like that. If weight and volume aren’t a big issue then you have way more options. Polyester fill bags can be a bit bulky but are exceptionally warm and much more affordable than natural down fill. Also, get a silk or wool sleeping bag liner. They add a few degrees of warmth but also make the bag way more comfortable against your skin. Way way more comfortable. And you can wash the liner as needed without the whole operation of washing the bag.