If the only evidence came from a stop that should never have been made, then yes, it may be possible to get the case dismissed: if the stop was illegal, the evidence from the stop can be excluded, and if there is no more evidence, the charges should be dismissed (either voluntarily by the state, or by the judge at trial if the state has insufficient evidence to sustain them). Getting evidence excluded from a stop is NOT an easy thing: it takes familiarity with the rules of evidence, with cases applying those rules, an attention to the relevant details, and the ability to argue persuasively. Since so much is riding on the outcome and your mother has a valid-seeming defense, she should hire a criminal defense attorney to represent her and move to exclude the evidence.