Sammy has been chewing a lot lately.

Honestly, if you can put up with it a bit longer, the best cure is ignoring Nixie completely. I mean, if you’re in the room and she chews, walk out. If she’s trying to get your attention from elsewhere, do NOT go in to her when she does it. I also say Shhh! Shhhh! from another part of the apt. and then don’t do anything else. The idea is to reinforce that chewing on bars does not get her what she wants.

If she wants out, and that’s usually it, when she’s been quiet a few minutes or more, go in and let her out soon, praising her. If she starts to chew, leave again.
I’m guessing she’s just not getting enough exercise when she’s in the mood. First thing in the morning they are most active, so that’s the best time for a run, then at dusk. Also, if her cage smells or is messy due to older litter, she’s telling you to clean it up for her. That’s kind of a legitimate complaint (I speak from experience.). One night she was chewing frantically and I ignored her for quite a while but she wouldn’t stop. I finally thought there was something wrong, and sure enough, her litter pan had spilled and it was a serious mess mixed in the water. She was miserable. I cleaned it all up and she watched me while sitting right next to me, then hopped back in happily when it was nice again. No more chewing.

Oh, and sometimes they chew to alert you about something. Like if a dog is barking outside, she’s worried inside and is telling you there’s danger.

Pam hit the nail on the head. Usually bar chewing is an attempt to get attention – even you looking at her, or talking to her, is giving her attention. Ignoring the problem and rewarding her when she’s good (by letting her out or giving a treat) will help.