Very annoying but I would just get on and do it but, as Cathy S says, make sure that it's known you're resolving something started by another. It wouldn't hurt to contact the other person and see if she has anything helpful she can add to the mix - perhaps point you in the right direction to get it cleared up.
I've had to deal with similar stuff in the past - it's all part & parcel of taking on a new job. Annoying having to clear up someone else's mess but par for the course.
And of course, brownie points with the new boss when it's all sorted professionally and efficiently!
Good luck! And hope the new boss is going to be easy to kick into shape
