In my opinion, there is no point in discussing who selected her, why she was selected, or the possibility of a wrong selection at this juncture. The focus now should be on her professionalism and code of conduct. It is possible for any of us to encounter a similar situation after hiring an employee, even if they seemed the best fit during the interview.
You may want to speak to her in person, make her aware of the issues that concern you, and counsel her appropriately. If this has already been done, you may consider issuing a final warning in writing, specifying the areas for improvement and setting a specific timeframe for correction, perhaps one month. It would be beneficial to document references to previous discussions, verbal warnings, and counseling sessions you have had with her. Monitor her behavior closely during this observation period and provide any necessary support to help her meet expectations. Clearly state in the final warning letter that Management reserves the right to terminate her employment if she does not take the warning seriously and continues to exhibit the same behavior. Keep a copy of this letter duly acknowledged by the employee in her personal records.
If the issues persist despite counseling, final warnings, and support provided, retaining her may not be advisable. You can request her to resign voluntarily after the deadline or terminate her employment by providing one month's notice payment.
Regards,
HR Professional.