Employee chatting on Whatsapp - is it okay to monitor?

Dear All, I see that one employee is always with her mobile chit chating in whatsapp, is it good to monitor them or shall i leave it like that. Because i feel that more on work, her concentration is on her mobile more. but she does work too.
I have informed earlier to my HR Head, he given me the permission to warn her from my end, i even told her politely, even then not listening to it. Kindly advice me as an HR, can I call her and talk to her or should i ignore it or should i inform to her Team Leader. Her role is a junior Software developer, she joined recently 6 months back.
THanks & Regards,
Vidhya- HR

I think time has come to seriously warn her (orally) as she has paid no heed to your earlier attempt. The continuous chit chat distracts her as well as others in their jobs, particularly in a field like software development.

Did you receive any complaint from the Team leader or her manager about her work? if so you can ask the Team Leader or Manager to call and counsel her. If there are no complaints against her about her work, you can let the Team leader or the Manger know your observation of her spending time on mobile and ask him to advise her to desist from doing so as the habit may catch up with others. In the fist instance, put the onus on her team leader of manager .
B.Saikumar
HR & Labour Relations Adviser
Navi Mumbai

Team leader is the ideal person to counsel or advice her.
HR can at best inform team manager/leader about her actions and leave it to be handled at team level, unless off course other teams are getting afflicted by whats up disease.