I've kept a small mandarin in a RSM 130 for almost two years without a refugium. I keep the ceramic tubes that come with the RSM in the rear sump under the skimmer. They're loaded with pods and the pods get sucked out to the display. Occasionally I'll buy a chunk of chaeto and shake it out in the rear sump to repopulate the pod and critter population. If you've also kept a mandarin for two years, your refugium is doing the same at keeping the pod population up. Use it to grow some cheato or other macroalgae like blue ochtodes for even better results.
Over the two years mine has gone from near death skinny (that's how she arrived at the LFS) to slightly plump. I've debated getting her to eat frozen, but most I've seen that eat frozen are fat and lazy, and I like watching her hunt.
If you can catch her easily (probably best to try at night while she's in her "cocoon"), put her in the refugium for a little while and observe the result. There could be something in else in the tank stressing her.
There's probably nothing to worry about, but if she's getting really skinny (pinched stomach), then taking some kind of action before she doesn't have enough energy to hunt is a good idea. Some alone time in the refugium could be just what she needs. Also, the walls may be less reflective so if she's really staring at herself in the mirror, that would break the spell.
Good luck!
One thing I've observed that may help with pod population is keeping iodine levels up. Pods release eggs when they molt, and iodine appears to help molting. I add two or three drops of Lugols solution each week. Shortly after I'll see pod molts in the skimmer cup.
