You give her time, that's what you do. If she was in as bad a relationship as you say, it would be best if you let her be and be there for her. In time, she will heal and you'll be there, only then can you talk about another relationship.
you are in the perfect situation! comfort her and b on her said. always agree with what she says and b there for her. if shes hurting be nice ( BUT DONT FLIRT ). she clearly isnt ready to jump back into a nother reealshionship yet. shes been hurt too many times. and maybe even by dating her you will most likely hurt her in the end so be her best guy friend ( DONT B A BOYFRIEND ) that's what she really needs! if she sees that your there for her and she can trust her then yeah go for it date her! but remember in the end you will hurt in like all the other guys. so if you do date her and you wanna dump her wait untill she dumps you because then she will dump you and you wont get hurt ( that is of course if she dumps you and u still have feelings or u grow your feelings back ) but then after you guys are done then it might be no friends or you can ease yourselves back into friendship