My best thing is to touch and play with things in my hands. Some of them really relieve my stress, although have never been one for the rigid stress balls...too hard to squish for me to relax out. We used to have a "Popping Peepers Cow "(i think sold in stores and also online for a few dollars.) But there are probably less expensive versions of various textures and colors that one could buy in a dollar store. Depending on the person they may also like a slinky or some smooth river rocks to hold.
I also like fuzzy blankets/throws. Have one on my bed right now that I snuggle up to my face when needing to bring on calm or go to sleep. As long as it is a neutral or pastel color than that works best to keep my sensory input low.
There are some people that use a 25-watt bluish colored light bulb that is supposed to help reduce stress, but honestly they seemed to mess with me more (could try though since they are only $3). For me, perhaps a well shaded lamp shade or a 25-watt bulb in regular light color would be best.
Last but not least a small fountain (can buy cheap at store) or a little sized aquarium with soothing water sounds could help. It does calm me down. I hear other people like those sound machines with waterfalls, natural sounds, etc.
Hope you are able to find some things that she likes. Maybe ask her what she likes to get herself to her calm/happy place and go from there. And, in the event that she does want to try a few new things out...might be a good idea to just hold on to the receipts in the event that an exchange or refund is needed on some items.
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Your Aspie score: 154 of 200
Your neurotypical (non-autistic) score: 56 of 200
You are very likely an Aspie
AQ Test Score: 37