My niece needs a bag for camping for college geology class trips. She is going to Wisconsin in March and South Dakota/Yellowstone in May. She thinks a 20 degree bag would be about right. This is not for backpacking, so weight and size are not really a concern. I bought the REI Lyra, but it is too snug on her. She probably needs a bag with a girth of 65 inches or more, and she is 5'5.5" tall.

Any recommendations? Most of the women's bags look too narrow. Most of the "20 degree" bags I've seen do not look like they have near enough loft to be warm at that temperature. She also told me that she can't sleep when she's hot, so I don't want to go too low with the temperature rating either. Price was somewhat of a consideration, but at this point I need to spend enough to get something that will work.