We used an Aegismax sleeping bag on our recent trip, and it performed fine. Quite a debate could be had about ethical down, sources of same, etc, but despite my initial hesitation of buying direct from China for a few reasons–sadly, so much is produced in China and there is not always a guarantee that you’re getting what the Western based companies say you’re getting unless they hold to some pretty strict requirements.
I went with them because it didn’t seem to be an obvious rip off of another company’s product–that and the price and seeming higher quality of the materials (which so far, have borne out except the sewn through design of baffles). Some people here have said that they have copied other products though–i wasn’t and am not directly aware of those.
But another potential issue is quality control. Just because the bag we bought and have used works well, doesn’t necessarily mean that all those models will.
Probably a moot issue, since that particular bag is rated to around 46 degrees. There are other brands and models on Alexiexpress that sell warmer bags. Many of these are also on Amazon, so i would read the reviews there if considering.
Another option is paying a little bit more for an EE short and slim quilt (assuming your sister is not much larger than the average) and sewing a sleeve of wind resistant fabric onto the bottom. I did that with one of my winter quilts (M50 material, very wind resistant), and to me, it’s the best of both worlds of quilts and bags–almost the lightness and packability of a quilt, but cuts drafts, wind, etc better than a traditional quilt (i can also increase the warmth with inserting Apex in the sleeve if i want). These cost 240, but only weigh about 16 and a half ounces (but with some UL fabric sewn on the bottom, will gain about a half ounce or so more).