Is it okay to sell dietary supplements as pain medication?

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My mother has back pain, so she went to the pharmacy....
She was prescribed this supplement (Circle For You Selenium) along with some painkillers.
However.... this supplement is a dietary supplement, not a painkiller.
When I search for it, only things like "antioxidant effects" come up.
She has osteoporosis, so she needs to take osteoporosis medication and get injections for her back pain...
But she went to the pharmacy and brought those back.
She says her back stopped hurting after taking that supplement and the painkillers.
Now she refuses to go to the orthopedic clinic. She says that supplement is effective and insists on only taking that.
Is there a way I can ask the pharmacist to explain this clearly to her?
I called them....
They said that the supplement is effective for pain. Even though it's not in the manual...
(They said they legally cannot write such things down.)
They said it is effective.
She really needs to go to the orthopedic clinic to get an examination...
I'm so worried.ㅠㅠ