It depends on her circumstances. I was predicted up from my AS grades in 2 of my subjects from a B to an A and a C to an A. In both cases, I achieved the A so it is certainly possible to increase by 2 grades if you put the work in. However, 3 grades is a LOT.
Also I had extenuating circumstances which were submitted to the universities by my school which explained why I underachieved at AS level. I would say if there was nothing mitigating around her A levels, then the universities will look extremely closely to try and work out why she has been predicted so highly.
To be honest I would just focus on yourself. Despite applying for the same course, her application isn't going to affect yours.