Work problems! Please help.

So I just started working somewhere around a couples months / year ago. The last girl that was in my position worked in my position for 3-4 years and then got promoted so higher pay etc & is now having troubles at work because apparently there’s no work for her anymore and she’s left with nothing to do. Another colleague of mine told me that in 2 weeks things are gonna change and her or someone else would be fired. I ’m just very paranoid for my job at the moment, for a couple months my position was vacant as she got promoted, so I looked online & my position was advertised and I got the job. I am just paranoid if she can get demoted & then I lose my job even though they already filled the opening. Can anyone help me?