I agree you HAVE to make the first move. I know its hard but start small...try by asking her what time it is and/or how was her weekend...then work your way up to bigger quetions...asking if you know if someone (any person you both know) is in work today or if you know if she/they are going to happy hour on Friday night, etc. if you don't work in the same building...then try to meet her where she has lunch, accidentally of course
Its hard when they are this shy and avoiding you, its difficult for you i know and frustratting but if she is worth it...go for it!!!!!