Honesty, I think it's not your responsibility to tell her anything....Her manager should tell her....
I think you are focusing on her actions too much and it's getting into you....
Just ignore her....her behavior is not your responsibility and if you tell her something, you just make things worse.....just stay away from trouble and concentrate on your job....
I usually don't care what people are doing at work if there are not under my vision....I don't care when they are coming to work if they are calling sick or not....these are not my concern....I have to do my job, that's my responsibility....that's all....
stay cool and away from her, then things will go good
take care
Marjan