Glass in a inert substance, it does not react with anything in the body. It does not cause any inflammatory response.
Since the glass particles were small enough to fit inside a capsule, they are not big enough to cause any problems in the bowel. The capsule will dissolved, the glass particles will pass into the small intestine with the rest of the stomach contents. They will get mixed into the stool and be passed through the body. They will be eliminated with the rest of the fecal matter.
Don't worry too much about the glass itself. The question is, why did she do it in the first place? Was it a prank, or was she seeking attention, or was she trying to harm herself? If it was the latter, then she needs psychological help.