One of my colleagues has always been a slacker, extremely confident/cheeky though so everyone is afraid of her. I've always stayed our of her way and never had much 'trouble' with her apart from always having to pick up her work. Sometimes when we have 'applications' that are linked, she will always without fail hold onto hers until i ask for it, so i have to do her work. Normally everyone just pitches in and we all take turns asking for any linked work but she never asks for anyone's. I got fed up recently and held onto one for 2 months (im part time) to see if she would ask for it and she didnt. She kept extending the Bf date until i asked for it. I emailed her and asked if she was working on it because she added the date, she said no it was because there was a pause on that work at the minute (it finished the week before). I emailed our senior manager as my manager was off at the time (and is also friends with this colleague). To mention how she hasnt asked for one of my applications for almost 2 years so i end up doing hers. I asked for it to treated confidentially and somehow she has found our it was me that said something . Now my manager and all her friends are taking a tone with me, highlighting any 'mistakes' i make to senior management (i was bcc into the email by my manager), pushing more work onto me. Before this i was told my work was excellent. Several other colleagues in the office spoke about this lazy colleague and one had told me 2 of them had raised it before, one with my manager (allegedly, but i now don't think they did at all). It was a frequent topic of conversation/knowledge about this co worker but now im the target. Any advice?