No, she can't just ignore the JC since the elder's book instructs them can go ahead and carry out the proceedings even without the accused present. Once a JC is formed it's almost impossible to get it cancelled, however, here are some options:
-There is a loophole in the elder book that says that if after various attempts they can't reach the person in question to arrange the judicial committee date, they should just leave the matter pending. So one might attempt going into hiding for a few months, not answering any calls, and hoping the elders would just forget. If your cousin has already spoken to the elders, then it's too late for this method.
-If there was only one witness to her alleged smoking, she can deny the accusation and the elder's would not be able to proceed with a JC so long as they don't have 2 witnesses nor a confession.
-If she doesn't want to get DF, she can go into the meeting, put some pepper spray in her eyes, shed a few tears, tell the elders that she's so embarrassed that she "hurt her relationship with Jehovah by smoking", that she only smoked a few of them in a moment of weakness, and that she never ever ever wants to hurt Jehovah again like that. Maybe they'd only privately reprove her in this situation.