This.Does she have anything she should be doing?
I know plenty of people that at one time or another had nothing to do and spent their days surfing the net. If she's not in a "professional" position you can't really blame her for not pestering her boss for more tasks or pro-actively undertaking some personal development.
On the other hand if she failing to complete work and causing others or yourself more work you should be complaining.
Is she is missing work, that you or others are having to pick up have a word.
She may just be a better worker than you & completing the tasks sooner, leaving her time to browse until her next lot of work is given.
Also, are you doing enough work? - it sounds like you are watching the screen of the girl who sits next to you all day like some creepy stalker
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