What do you do when your human resource person is biased?:
There is an old adage:  "Sunlight is the best disinfectant".

If you openly confront this woman, you are facing an all-out war.  She will despise you for having exposed her misdeeds.  If you anonymously send the General Manager proof of her actions, he may be inclined not to believe the accusations.

You could have a meeting with the General Manager, and ask for anonymity.  However, you must have all your facts completely established.  Getting people to write their opinion will not be accepted as fact.

You need absolute proof, and to show her INTENT to cheat and lie.  She can always claim these were innocent mistakes or things done without her knowledge.

Remember, you will need verifiable dates, names, events, and most importantly, a CONSISTENT story from each person who was a witness to any of these events.

You do not want to come across as a whining malcontent.  If you show indisputable proof, the General Manager will have to act.