I am a graduate and I have been in my job a year, another graduate joined 6 months ago. Whilst I have a lot more experience than her, lately she has talked down to me and is telling me how I should do my job. She has told my manager that me and another guy come in late (which we don't) and had a go at me for leaving the department with no cover over lunch which I told her it was someone else who walked out after I had gone but she was having none of it.

She has been shadowing other people a lot on visits and when I mentioned I will be doing it she seemed threatened. I have seen her emailing people all day at work and not doing her work whilst she is making up stories about me just so she can get ahead. My manager even said that this girl is quite vocal and people are starting to notice. I just don't want lies going around when I am trying to work hard to do well in my career. What is the best approach?