I'm a big fan of the Enlightened Equipment brand. They don't carry them at REI, but they are custom made, super light, and are super comfy. They specialize in "camping quilts" so they aren't mummy bags, but they can be used like a cape while bumming around camp in the AM or PM too. My wife has the 10 degree version. I have the 20 degree.
I have the Cats Meow too and it usually works fine for me. One thing is that I would like it to be more crushable to save space for backpacking. It stays pretty bulky.
I get warm really easily when I hike, but I also get really chilled when I stop. So I tend to want a warmer bag than some people. Adding water bottles or extra layers doesn't solve that for me - a warmer bag is best. So knowing what you need helps.
I have a couple of older REI Joule women's mummy bags. I like them a lot. I chose them because they are warm but quite lightweight, and weren't ultra expensive. I can pack those things into a tiny stuff sack if I really try. The downside to them is the mummy part. They (like most mummy bags) are kind of claustrophobic unless I'm really cold.
Currently I'm considering getting a Nemo, especially one of the 15 degree rated women down bags. I tried one in the store the other day, and love it. It has so much more room (I'm also a side sleeper), but enough down that I think it will be warmer than my Joule bags. But it's almost a pound heavier - mostly in more down - which will only be worth it when it's colder.
Don't forget that once you find a bag you like, you may be able to find it in the Used Gear or Outlet areas of REI!