I would be very careful. I definitely would not sit her down and discuss her perceived problem and if most of this drinking problem is heresay then she may believe no one has any suspicion of her issue whatsoever. Even the inappropriate phone calls and texts can not definitively prove she was drunk. We in recovery have a heightened awareness of this disease and I'd hate to have this fact come back and bite you in the ass. Her denial could be so strong that she may file a complaint against you that you are proliferating office gossip and slandering her. For now, I would just document everything.